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  • 1.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Moreno, Sergio
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Vacuum infusion of cellulose nanofibre network composites: Influence of porosity on permeability and impregnation2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 95, s. 204-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Addressing issues around the processing of cellulose nanofibres (CNF) composites is important in establishing their use as sustainable, renewable polymer reinforcements. Here, CNF networks of different porosity were made with the aim of increasing their permeability and suitability for processing by vacuum infusion (VI). The CNF networks were infused with epoxy using two different strategies. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated. Calculated fill-times for CNF networks with 50% porosity were the shortest, but are only less than the gel-time of the epoxy if capillary effects are included. In experiments the CNF networks were clearly wetted. However low transparency indicated that impregnation was incomplete. The modulus and strength of the dry CNF networks increased rapidly with decreasing porosity, but their nanocomposites did not follow this trend, showing instead similar mechanical properties to each other. The results demonstrated that increasing the porosity of the CNF networks to ≈ 50% gives better impregnation resulting in a lower ultimate strength, a higher yield strength and no loss in modulus. Better use of the flow channels in the inherently layered CNF networks could potentially reduce void content in these nanocomposites and thus increase their mechanical properties.

  • 2.
    Alam, Md. Minhaj
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Tuominen, J.
    Tampere University of Technology, Department of Materials Science.
    Vuoristo, P.
    Tampere University of Technology, Department of Materials Science.
    Miettinen, J.
    Tampere University of Technology, Department of Mechanics and Design.
    Poutala, J.
    Tampere University of Technology, Department of Mechanics and Design.
    Närkki, J.
    Tampere University of Technology, Department of Materials Science.
    Jankala, J.
    Technology Centre KETEK Ltd..
    Peltola, T.
    Technology Centre KETEK Ltd..
    Barsoum, Z.
    Royal Institute of Technology, Department of Aeronautical and Vehicle Engineering, Stockholm.
    Analysis of the stress raising action of flaws in laser clad deposits2013Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 46, s. 328-337Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue cracking of laser clad cylindrical and square section bars depends upon a variety of factors. This paper presents Finite Element Analysis (FEA) of the different macro stress fields generated as well as stress raisers created by laser cladding defects for four different fatigue load conditions. As important as the defect types are their locations and orientations, categorized into zero-, one- and two-dimensional defects. Pores and inclusions become critical close to surfaces. The performance of as-clad surfaces can be governed by the sharpness of surface notches and planar defects like hot cracks or lack-of-fusion (LOF) are most critical if oriented vertically, transverse to the bar axis. The combination of the macro stress field with the defect type and its position and orientation determines whether it is the most critical stress raiser. Based on calculated cases, quantitative and qualitative charts were developed as guidelines to visualize the trends of different combinations.

  • 3. Alam, Md. Minhaj
    et al.
    Karlsson, Jan
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Generalising fatigue stress analysis of different laser weld geometries2011Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 32, nr 4, s. 1814-1823Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two-dimensional elastic-plastic finite element analyses was carried out on a laser welded box beam in order to study the impact of the geometrical aspects of the joint type and weld root on the fatigue stress behaviour. Different experimental and hypothetical weld geometries were studied. Characteristic root shapes, measured by the plastic replica method, and critical geometrical aspects were classified and then studied by FE-analysis with respect to their impact on the maximum stress. The simulation of hypothetical transition geometries facilitated the identification of trends and the explanation of part of the phenomena. However, quantitative geometry criteria were only partially suitable to describe the relations. The results have shown that the combination of throat depth, local surface radius and its opening angle determines the peak stress value and its location. Beside extended throat depths, particularly larger toe radii and the avoidance of small opening angles and of surface ripples reduces the peak stress. The explanations were developed in a generalising manner, accompanied by illustrative and flow chart description.

  • 4.
    Alimadadi, H.
    et al.
    Chalmers University of Technology.
    Ahmadi, M.
    University of Tehran.
    Aliofkhazraei, M.
    Tarbiat Modares University.
    Younesi, S.R.
    Royal Institute of Technology (KTH).
    Corrosion properties of electrodeposited nanocrystalline and amorphous patterned Ni–W alloy2009Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, ISSN 0261-3069, Vol. 30, nr 4, s. 1356-1361Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nickel-tungsten with satisfactory corrosion properties is a promising alloy to replace hard chromium. Relatively high adhesion between copper substrate and electrodeposited Ni-W alloy results in patterned morphology due to crack formation. In this work, corrosion resistance of patterned Ni–W alloys comprising 0-26 at.%.W were studied by potentiodynamic polarization and EIS in a medium containing Cl-. It is shown that corrosion resistance of single phase Ni-W is superior to amorphous and dual phase coated layers. It is also found that crack density is the dominant affecting factor on corrosion resistance of amorphous Ni-W alloys.

  • 5.
    Andres, Britta
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Blomquist, Nicklas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Cellulose binders for electric double-layer capacitor electrodes: The influence of cellulose quality on electrical properties2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 141, s. 342-349Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose derivatives are widely used as binders and dispersing agents in different applications. Binders composed of cellulose are an environmentally friendly alternative to oil-based polymer binding agents. Previously, we reported the use of cellulose nanofibers (CNFs) as binders in electrodes for electric double-layer capacitors (EDLCs). In addition to good mechanical stability, we demonstrated that CNFs enhanced the electrical performance of the electrodes. However, cellulose fibers can cover a broad range of length scales, and the quality requirements from an electrode perspective have not been thoroughly investigated. To evaluate the influence of fiber quality on electrode properties, we tested seven samples with different fiber dimensions that are based on the same kraft pulp. To capture the length scale from fibers to nanofibrils, we evaluated the performance of the untreated kraft pulp, refined fibers, microfibrillated cellulose (MFC) and CNFs. Electrodes with kraft pulp or refined fibers showed the lowest electrical resistivity. The specific capacitances of all EDLCs were surprisingly similar, but slightly lower for the EDLC with CNFs. The same electrode sample with CNFs also showed a slightly higher equivalent series resistance (ESR), compared to those of the other EDLCs. Graphite dispersions with MFC showed the best dispersion stability. 

  • 6.
    Asnafi, Nader
    Gränges Technology, Finspång, Sweden.
    Springback and fracture in v-die air bending of thick stainless steel sheets2000Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 21, nr 3, s. 217-236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this investigation, the attention is focused on the springback and fracture of thick stainless steel sheets. Nine different stainless grades and various thickness are tested. The thinnest sheet is 7.9 mm, whilst the thickest sheet is 31.3 mm. A consistent analytical model is constructed for prediction of the springback, the inner sheet radius prior to and after unloading, and the smallest die width. The springback calculated by this analytical model is in all cases smaller than that found experimentally. The correspondence between theory and practice, is however, very good, although the shift in the position of the neutral axis and thinning are neglected in the theoretical analysis. Fracture did not occur in any of the conducted bending operations. It is commonly assumed that fracture in v-die bending is related to the reduction in the cross-section area at fracture, Z, in tensile testing. Z was greater than 70% for the majority of the studied materials. It is shown that particularly the mode of fracture (fracture through shear bands or by necking) should be studied in future investigations.

  • 7.
    Belov, Ilja
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Zanella, Caterina
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Edström, Curt
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Finite element modeling of silver electrodeposition for evaluation of thickness distribution on complex geometries2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 90, s. 693-703Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper reveals benefits of multi-disciplinary computer simulation and parametric studies in the design of silver plating process for improved coating distribution. A finite element model of direct current silver plating is experimentally validated for an Assaf panel without agitation. The model combines tertiary current distribution with Butler–Volmer electrode kinetics and computational fluid dynamics at a very low flow-rate. The effect of charge transfer coefficients on the throwing power of the process is quantified for the studied geometry, and variation of cathodic current density and exchange current density is investigated. A simpler model based on secondary current distribution is employed to quantify the effect of electrolyte conductivity on the throwing power of the process. A model combining tertiary current distribution and computational fluid dynamics has been developed and experimentally validated for simulation of complex telecom component electroplating in agitated electrolyte. The effect of current density on the process throwing power is quantified. Recommendations regarding modeling methodology and the effect of electrochemical and process parameters on the thickness distribution have been developed.

  • 8.
    Belov, Ilja
    et al.
    Jönköping University, Sweden.
    Zanella, Caterina
    RISE., SP – Sveriges Tekniska Forskningsinstitut. Jönköping University, Sweden; University of Trento, Italy.
    Edström, Curt
    Jönköping University, Sweden.
    Leisner, Peter
    RISE., SP – Sveriges Tekniska Forskningsinstitut. Jönköping University, Sweden.
    Finite element modeling of silver electrodeposition for evaluation of thickness distribution on complex geometries2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 90, s. 693-703Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper reveals benefits of multi-disciplinary computer simulation and parametric studies in the design of silver plating process for improved coating distribution. A finite element model of direct current silver plating is experimentally validated for an Assaf panel without agitation. The model combines tertiary current distribution with Butler-Volmer electrode kinetics and computational fluid dynamics at a very low flow-rate. The effect of charge transfer coefficients on the throwing power of the process is quantified for the studied geometry, and variation of cathodic current density and exchange current density is investigated. A simpler model based on secondary current distribution is employed to quantify the effect of electrolyte conductivity on the throwing power of the process. A model combining tertiary current distribution and computational fluid dynamics has been developed and experimentally validated for simulation of complex telecom component electroplating in agitated electrolyte. The effect of current density on the process throwing power is quantified. Recommendations regarding modeling methodology and the effect of electrochemical and process parameters on the thickness distribution have been developed.

  • 9.
    Björklund, Stefan
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Goel, Sneha
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Function-dependent coating architectures by hybrid powder-suspension plasma spraying: Injector design, processing and concept validation2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 142, s. 56-65Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The attractive properties achieved by Suspension Plasma Spraying (SPS), combined with the availability of high throughput capable plasma spray systems that permit axial feeding, provide encouragement to explore use of suspensions for next generation functional applications. This paper deals with realization of coatings with various pre-determined function-dependent architectures by employing a hybrid powder-suspension feedstock. Some illustrative application-relevant coating architecture designs are discussed, along with the specific benefits that can accrue by deploying a multi-scale powder-suspension feedstock combination. An elegant feedstock delivery arrangement to enable either simultaneous or sequential feeding of powders and suspensions to enable convenient processing of coatings with desired architectures is presented. As proof-of-concept, deposition of layered, composite and functionally graded coatings using the above system is also demonstrated using appropriate case studies

  • 10.
    Borkar, Hemant
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Seifeddine, Salem
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    In-situ EBSD study of deformation behavior of Al-Si-Cu alloys during tensile testing2015Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 84, s. 36-47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study deals with the microstructural aspects of the deformation behavior in Al-Si-Cu alloy A380. This has been carried out with in-situ tensile testing coupled with EBSD analysis. The alloy specimens having different microstructures with two different secondary dendrite arm spacing (SDAS) of 9 µm and 27 µm were produced by the unique gradient solidification method. The study of misorientation distribution and texture evolution was performed with different tools in EBSD analysis. The texture was not significantly affected by deformation in both types of alloy specimens. With increase in the deformation, the microstructures are characterized by degradation of EBSD patterns and generation of substructures including low angle boundaries (LABs) and high angle boundaries (HABs). In both the microstructures with low and high SDAS, the boundaries were concentrated around eutectic phases; however this behavior was more pronounced at higher SDAS. The increase in the fraction of LABs with deformation was much higher in the microstructure with higher SDAS than with lower SDAS. This localized strain concentration was especially attributed to the large and elongated eutectic Si particles and Fe-rich intermetallics. The lower mechanical properties obtained at higher SDAS are the result of inhomogeneous strain distribution in the microstructure.

  • 11. Bressi, Sara
    et al.
    Dumont, A. G.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Carleton Univ, Ottawa, Canada.
    An advanced methodology for the mix design optimization of hot mix asphalt2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 98, s. 174-185Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The bitumen quantity to add to asphalt mixtures depends on the surfaces of aggregates and filler to be coated. The formulas currently available in the literature have limitations such as considering all the fillers with the same specific surface or the aggregates with spherical or cubical shapes. This paper aims to define an analytical approach for the determination of the optimal dosage of bitumen in HMA proposing new methodologies to go a step further in the resolution of the above mentioned approximations. Indeed, new surface area factors were calculated to determine the aggregates surface considering their real shapes and volumes. Afterwards, the authors proposed a detailed characterization of two types of fillers and the critical filler concentration, introduced by Faheem and Bahia, was used to calculate the minimum amount of bitumen for maintaining the mastic in a diluted state and filling the voids in the mixtures. Finally, a verification of the formula developed was carried out with specific laboratory tests. These results allow the challenge of revising the method of calculating the specific surface of the aggregates and filler to be addressed with the final goal to include them in a new mix design optimization for HMA. 

  • 12.
    Carlsson, Bo
    Högskolan i Kalmar, Naturvetenskapliga institutionen.
    Selecting material for the exterior panel of a private car back door by adopting a total cost accounting approach2009Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 30, nr 3, s. 826-832Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A total cost accounting approach for material selection is demonstrated by analysing the suitability of some light weight materials for use in the exterior panel of a back door to a private car. For pre-selection purposes, the suitability of using low alloy steel, aluminium, SMC and a hybrid GMT/aluminium material as construction material for the exterior panel of the back door are compared by taking into account differences in production cost, cost associated with excess mass, cost of probable failures and damages, maintenance and operational costs, end-of-life cost, and cost associated with probable ecological damage. From one manufacturer's point of view and considering only the production cost for the installed part of the back door, steel is the best alternative for large production volumes. However, this is not the case when taking into account all costs. All the other materials seem better and exhibit essentially the same qualities. The main reason is lower fuel consumption. The results of the suitability analysis nicely reflect the relative importance of the various factors contributing to the total cost but the suitability analysis also points to the need of performing a more advanced analysis taking into account also aspects like safety and ease of surface treatment.

  • 13.
    Carosio, Federico
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cuttica, Fabio
    Medina, Lilian
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Clay nanopaper as multifunctional brick and mortar fire protection coating: Wood case study2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 93, s. 357-363Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract Wood is one of the most sustainable, esthetically pleasing and environmentally benign engineering materials, and is often used in structures found in buildings. Unfortunately, the fire hazards related to wood are limiting its application. The use of transparent cellulose nanofiber (CNF)/clay nanocomposites, with unique brick-and-mortar structure, is proposed as a sustainable and efficient fire protection coating for wood. Fire performance was assessed by cone calorimetry. When exposed to the typical 35 kW/m2 heat flux of developing fires, the time to ignition of coated wood samples increased up to about 4 1/2 min, while the maximum average rate of heat emission (MARHE) was decreased by 46% thus significantly reducing the potential fire threat from wood structures.

  • 14.
    Celma Cervera, Carlos
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. bEMPA Swiss Federal Laboratories for Materials Testing and Research, Switzerland.
    Larsson, Per-Lennart
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Contact-induced deformation and damage of rocks used in pavement materials2017Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 133, s. 255-265Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Performance of stone-based construction materials, such as asphalt and unbound aggregate mixtures is defined to a great extent by the mechanics of the stone-to-stone interactions. Accordingly, the Discrete Element Method (DEM) is gaining popularity as a modelling tool to investigate the mechanical behavior of these materials. Contact and failure laws defining particles force-displacement relationships and the propensity of particles to break are crucial inputs for the DEM simulations. The present study aims at providing an experimental contact mechanics basis for the development of physically based stone-to-stone interaction laws. The attention is focused on investigating stone's force-displacement relationship and damage characteristics at pure normal loading for two stone materials used by the road industry. Experiments are performed at spherical contact profiles for cyclic and monotonically increasing loads. The emphasis lies on the evolution of contact compliance and accumulation of contact induced damage. The effect of surface roughness on the materials response is examined through comparative experiments performed on the specimens with different roughness values. Optical and environmental scanning electron microscopy (ESEM) observations of the contact induced damage at the material surface are presented and discussed in the context of contact mechanics. The implications of the reported experimental findings on the development of mechanics based contact and failure laws for the DEM modelling of stone-based construction materials are discussed.

  • 15.
    Ceschini, Lorella
    et al.
    SMETEC Dept. University of Bologna, Bologna, Italy.
    Boromei, Iuri
    SMETEC Dept. University of Bologna, Bologna, Italy.
    Seifeddine, Salem
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Svensson, Ingvar
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Effect of Fe content and microstructural features on the tensile and fatigue properties of the Al-Si10-Cu2 alloy2012Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 36, s. 522-528Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As the automotive industry has to meet the requirements of fuel efficiency and environmental concerns, the use of aluminium alloys is steadily increasing. A number of papers have been published about the correlation between microstructure and mechanical properties of the widely used A356/A357 aluminium alloys, while relatively few data are available on others hypoeutectic Al-Si alloys, such as Al-Si-Cu alloys with higher Si content. In this work the effect of different amounts of Fe and Mn on the tensile and fatigue behaviour of the AlSi10Cu2 casting alloy was studied. The reason of this study comes from the fact that cast components are mostly made by secondary Al alloys that inevitably contain Fe, which in turn forms intermetallic compounds, negatively affecting the mechanical behaviour of the alloy. Fatigue specimens were subjected to hot isostatic pressing (HIP) before tests, in order to eliminate the internal pores (gas pores and interdendritic shrinkages) and therefore to solely investigate the effect of microstructural features, rather than solidification defects, on the fatigue propagation stage. The microstructural characterization of the alloy was carried out by optical and scanning electron microscopy. Proof and ultimate tensile strength, as well as fatigue life of the investigated alloy were greatly enhanced by high Fe and Mn content, which reduced the micro-crack propagation rate; on the contrary Fe, without Mn, negatively affected the elongation to failure.

  • 16.
    Ceschini, Lorella
    et al.
    Dept of Industrial Engineering (DIN), University of Bologa, Italy.
    Morri, Alessandro
    Dept of Industrial Engineering (DIN), University of Bologa, Italy.
    Morri, Andrea
    Industrial Research Centre for Advanced Mechanics and Materials, University of Bologna, Italy.
    Toschi, Stefania
    Dept of Industrial Engineering (DIN), University of Bologna, Italy.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Seifeddine, Salem
    Dept of Materials and Manufacturing, Jönköping University.
    Effect of Microstructure and Overaging on the Tensile Behavior at Room and Elevated Temperature of C355-T6 Cast Aluminum Alloy2015Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 83, s. 626-634Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present study was focused on the microstructural and mechanical characterization of the Al–Si–Cu–Mg C355 alloy, at room and elevated temperature. In order to evaluate the influence of microstructural coarseness on mechanical behavior, samples with different Secondary Dendrite Arm Spacing (SDAS) (20–25 μm for fine microstructure and 50–70 μm for coarse microstructure), were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated at T6 condition and at T6 with subsequent high temperature exposure (41 h at 210 °C, i.e. overaging), both at room and elevated temperature (200 °C). Microstructural investigations were performed through optical and electron microscopy.

    The results confirmed the important role of microstructure on the tensile behavior of C355 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Larger SDAS, related to lower solidification rates, modify microstructural features, such as eutectic Si morphology and size of the intermetallic phases, which in turn influence elongation to failure. Overaging before tensile testing induced coarsening of the strengthening precipitates, as observed by STEM analyses, with consequent reduction of the tensile strength of the alloy, regardless of SDAS. A more sensible decrease of tensile properties was registered at 200 °C testing temperature.

  • 17.
    Ceschini, Lorella
    et al.
    University of Bologna, Italy.
    Morri, Alessandro
    University of Bologna, Italy.
    Toschi, Stefania
    University of Bologna, Italy.
    Seifeddine, Salem
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Johansson, Sten
    Linköping University.
    Effect of microstructure and overaging on the tensile behaviour at room and elevated temperature of C355-T6 cast aluminum alloy2015Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 83, s. 626-634Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present study was focused on the microstructural and mechanical characterization of the Al–Si–Cu–Mg C355 alloy, at room and elevated temperature. In order to evaluate the influence of microstructural coarseness on mechanical behavior, samples with different Secondary Dendrite Arm Spacing (SDAS) (20–25 μm for fine microstructure and 50–70 μm for coarse microstructure), were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated at T6 condition and at T6 with subsequent high temperature exposure (41 h at 210 °C, i.e. overaging), both at room and elevated temperature (200 °C). Microstructural investigations were performed through optical and electron microscopy.

    The results confirmed the important role of microstructure on the tensile behavior of C355 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Larger SDAS, related to lower solidification rates, modify microstructural features, such as eutectic Si morphology and size of the intermetallic phases, which in turn influence elongation to failure. Overaging before tensile testing induced coarsening of the strengthening precipitates, as observed by STEM analyses, with consequent reduction of the tensile strength of the alloy, regardless of SDAS. A more sensible decrease of tensile properties was registered at 200 °C testing temperature.

  • 18.
    Choi, Young Won
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Dong, Zhihua
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Li, Wei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Schönecker, Stephan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Kim, Hansoo
    Korea Univ, Inst High Technol Mat & Devices, Seoul 02841, South Korea..
    Kwon, Se Kyun
    Pohang Univ Sci & Technol, Dept Phys, Pohang 37673, South Korea..
    Vitos, Levente
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Predicting the stacking fault energy of austenitic Fe-Mn-Al (Si) alloys2020Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 187, artikel-id 108392Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aluminum and silicon are common alloying elements for tuning the stacking fault energy (SFE) of high Mn steels. Today the theoretical investigations on the Fe-Mn-Al/Si systems using Density Functional Theory (DFT) are very scarce. In the present study, we employ a state-of-the-art longitudinal spin fluctuations (LSFs) model in combination with DFT for describing the magnetic effects in Fe-Mn based alloys at finite temperature. We find that the traditional DFT-floating spin results fail to explain the experimental trends. However, the DFT-LSFs approach properly captures the Al-induced increase and Si-induced decrease of the SFE of the base alloy in line with the room-temperature observations. This finding highlights the importance of LSFs in describing the Al/Si effects on the SEE of Fe-Mn based alloys. We point out that the effects of the non-magnetic Al and Si additions on the SEE are in fact determined by the magnetic state of the host matrix. In addition, we estimate the role of carbon addition in the alloying effects of Al and Si. The present results provide a convenient pathway to access the important mechanical parameters for designing advanced high-strength alloys.

  • 19.
    Choi, Young Won
    et al.
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.
    Dong, Zhihua
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.
    Li, Wei
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.
    Schönecker, Stephan
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.
    Kim, Hansoo
    Korea Univ, Inst High Technol Mat & Devices, Seoul 02841, South Korea.
    Kwon, Se Kyun
    Pohang Univ Sci & Technol, Dept Phys, Pohang 37673, South Korea.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden;Wigner Res Ctr Phys, Res Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary.
    Predicting the stacking fault energy of austenitic Fe-Mn-Al (Si) alloys2020Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 187, artikel-id 108392Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aluminum and silicon are common alloying elements for tuning the stacking fault energy (SFE) of high Mn steels. Today the theoretical investigations on the Fe-Mn-Al/Si systems using Density Functional Theory (DFT) are very scarce. In the present study, we employ a state-of-the-art longitudinal spin fluctuations (LSFs) model in combination with DFT for describing the magnetic effects in Fe-Mn based alloys at finite temperature. We find that the traditional DFT-floating spin results fail to explain the experimental trends. However, the DFT-LSFs approach properly captures the Al-induced increase and Si-induced decrease of the SFE of the base alloy in line with the room-temperature observations. This finding highlights the importance of LSFs in describing the Al/Si effects on the SEE of Fe-Mn based alloys. We point out that the effects of the non-magnetic Al and Si additions on the SEE are in fact determined by the magnetic state of the host matrix. In addition, we estimate the role of carbon addition in the alloying effects of Al and Si. The present results provide a convenient pathway to access the important mechanical parameters for designing advanced high-strength alloys. 

  • 20.
    Dai, J. H.
    et al.
    Royal Inst Technol, Appl Mat Phys, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden;Harbin Inst Technol Weihai, Sch Mat Sci & Engn, 2 West Wenhua Rd, Weihai 264209, Peoples R China.
    Li, W.
    Royal Inst Technol, Appl Mat Phys, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden.
    Song, Y.
    Harbin Inst Technol Weihai, Sch Mat Sci & Engn, 2 West Wenhua Rd, Weihai 264209, Peoples R China.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. Royal Inst Technol, Appl Mat Phys, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden.
    Theoretical investigation of the phase stability and elastic properties of TiZrHfNb-based high entropy alloys2019Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 182, artikel-id UNSP 108033Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First principles calculations are performed to study the effects of alloying elements (X = Al, Si, Sc, V, Cr, Mn, Cu, Zn, Y. Mo, Ta, W and Re) on the phase stability and elastic properties of TiZrHfNb refractory high entropy alloys. Both equimolar and non-equimolar alloys are considered. It is shown that the calculated lattice parameters, phase stability and elastic moduli of equimolar TiZrHfNbX are consistent with the available experimental and theoretical results. The substitutions of alloying elements at Ti, Zr, and Hf sites with various contents show similar effects on the phase stability and elastic properties of the TiZrHINb-based alloys. The substitutions on Nb site are found to generally decrease the stability of body centered cubic phase. Close connections between the charge densities at the Wigner-Seitz cell boundary and the bulk moduli of TiZrHfNb-based alloys are found. The present results provide a quantitative model for exploring the phase stability and elastic properties of TiZrHINb-based alloys from the electronic structure viewpoint. (C) 2019 The Authors. Published by Elsevier Ltd.

  • 21.
    Dai, J. H.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Harbin Inst Technol Weihai, Sch Mat Sci & Engn, 2 West Wenhua Rd, Weihai 264209, Peoples R China..
    Li, Wei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Song, Y.
    Harbin Inst Technol Weihai, Sch Mat Sci & Engn, 2 West Wenhua Rd, Weihai 264209, Peoples R China..
    Vitos, Levente
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Uppsala Univ, Dept Phys & Astron, Div Mat Theory, Box 516, SE-75120 Uppsala, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Theoretical investigation of the phase stability and elastic properties of TiZrHfNb-based high entropy alloys2019Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 182, artikel-id UNSP 108033Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First principles calculations are performed to study the effects of alloying elements (X = Al, Si, Sc, V, Cr, Mn, Cu, Zn, Y. Mo, Ta, W and Re) on the phase stability and elastic properties of TiZrHfNb refractory high entropy alloys. Both equimolar and non-equimolar alloys are considered. It is shown that the calculated lattice parameters, phase stability and elastic moduli of equimolar TiZrHfNbX are consistent with the available experimental and theoretical results. The substitutions of alloying elements at Ti, Zr, and Hf sites with various contents show similar effects on the phase stability and elastic properties of the TiZrHINb-based alloys. The substitutions on Nb site are found to generally decrease the stability of body centered cubic phase. Close connections between the charge densities at the Wigner-Seitz cell boundary and the bulk moduli of TiZrHfNb-based alloys are found. The present results provide a quantitative model for exploring the phase stability and elastic properties of TiZrHINb-based alloys from the electronic structure viewpoint. Elsevier Ltd.

  • 22.
    Davoodi, M.M.
    et al.
    Universiti Putra Malaysia 43400 UPM Serdang, Selangor.
    Sapuan, S.M.
    Universiti Putra Malaysia 43400 UPM Serdang, Selangor.
    Ahmad, D.
    Universiti Putra Malaysia 43400 UPM Serdang, Selangor.
    Aidy, A.
    Universiti Putra Malaysia 43400 UPM Serdang, Selangor.
    Khalina, A.
    Universiti Putra Malaysia 43400 UPM Serdang, Selangor.
    Jonoobi, Mehdi
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Concept selection of car bumper beam with developed hybrid bio-composite material2011Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 32, nr 10, s. 4857-4865Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Application of natural fibre composites is going to increase in different areas caused by environmental, technical and economic advantages. However, their low mechanical properties have limited their particular application in automotive structural components. Hybridizations with other reinforcements or matrices can improve mechanical properties of natural fibre composite. Moreover, geometric optimizations have a significant role in structural strength improvement. This study focused on selecting the best geometrical bumper beam concept to fulfill the safety parameters of the defined product design specification (PDS). The mechanical properties of developed hybrid composite material were considered in different bumper beam concepts with the same frontal curvature, thickness, and overall dimensions. The low-speed impact test was simulated under the same conditions in Abaqus V16R9 software. Six weighted criteria, which were deflection, strain energy, mass, cost, easy manufacturing, and the rib possibility were analyzed to form an evaluation matrix. Topsis method was employed to select the best concept. It is concluded that double hat profile (DHP) with defined material model can be used for bumper beam of a small car. In addition, selected concept can be strengthened by adding reinforced ribs or increasing the thickness of the bumper beam to comply with the defined PDS.

  • 23. Davydova, A.
    et al.
    Eriksson, J.
    Chen, R.
    Rudisch, K.
    Persson, Clas
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. University of Oslo, Norway.
    Scragg, J. J. S.
    Thio-olivine Mn2SiS4 thin films by reactive magnetron sputtering: Structural and optical properties with insights from first principles calculations2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 152, s. 110-118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thio-olivines such as (Fe,Mn)2(Si,Ge)S4 have been proposed as candidate earth-abundant materials for single and multi-junction solar cells. In this work we present the first investigation of Mn2SiS4thin films prepared by reactive magnetron sputtering deposition, using a composition grading approach. Precursor instability in ambient conditions is observed, revealing the oxidation/hydrolysis of Si–S bonds from the as-deposited film as a blocking mechanism for the ternary compound formation. Structural, morphological and optical properties of the annealed Mn2SiS4 films are reported for the first time. Resulting Mn2SiS4 films have orthorhombic Pnma structure and are polycrystalline. Raman active modes at 325 nm excitation are observed at 262, 320, 400 and 464 cm−1. From room temperature photoluminescence at 532 nm excitation the band gap is estimated to be about 1.9 eV, but a high optical absorption coefficient of >104 cm−1 was only obtained at E > 2.8 eV. First principles calculations are used for better understanding of opto-electronic properties. From the calculations, Mn2SiS4 is suggested to have a band gap of about 1.73–1.86 eV depending on the magnetic configuration of Mn and slight indirect nature. The slow absorption onset is interpreted by strong anisotropy due to one of the components of the dielectric function.

  • 24.
    Davydova, Alexandra
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Eriksson, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Chen, R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rudisch, Katharina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Persson, C.
    Univ Oslo, Dept Phys, Ctr Mat Sci & Nanotechnol, POB 1048, NO-0316 Oslo, Norway;KTH Royal Inst Technol, Dept Mat Sci & Engn, S-10044 Stockholm, Sweden.
    Scragg, Jonathan J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Thio-olivine Mn2SiS4 thin films by reactive magnetron sputtering: Structural and optical properties with insights from first principles calculations2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 152, s. 110-118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thio-olivines such as (Fe,Mn)(2)(Si,Ge)S-4 have been proposed as candidate earth-abundant materials for single and multi-junction solar cells. In this work we present the first investigation of Mn2SiS4 thin films prepared by reactive magnetron sputtering deposition, using a composition grading approach. Precursor instability in ambient conditions is observed, revealing the oxidation/hydrolysis of Si-S bonds from the as-deposited film as a blocking mechanism for the ternary compound formation. Structural, morphological and optical properties of the annealed Mn2SiS4 films are reported for the first time. Resulting Mn2SiS4 films have orthorhombic Pnma structure and are polycrystalline. Raman active modes at 325 nm excitation are observed at 262, 320, 400 and 464 cm(-1). From room temperature photoluminescence at 532 nm excitation the band gap is estimated to be about 1.9 eV, but a high optical absorption coefficient of > 10(4) cm(-1) was only obtained at E > 2.8 eV.First principles calculations are used for better understanding of opto-electronic properties. From the calculations, Mn2SiS4 is suggested to have a band gap of about 1.73-1.86 eV depending on the magnetic configuration of Mn and slight indirect nature. The slow absorption onset is interpreted by strong anisotropy due to one of the components of the dielectric function. 

  • 25.
    Deng, Dunyong
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Soderberg, Hans
    Sandvik Machining Solut AB, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    On the formation of microstructural gradients in a nickel-base superalloy during electron beam melting2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, s. 251-261Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electron beam melting (EBM) is one of the most widely used additive manufacturing (AM) methods for metallic components and has demonstrated great potential to fabricate high-end components in the aerospace and energy industries. The thermal condition within a melt pool and the complicated thermal cycles during the EBM process are of interest but not yet well-understood, and will significantly affect the microstructural homogeneity of as-manufactured nickel-base superalloy components. To establish the thermal profile evolution during electron beam melting of nickel-base superalloys, Inconel 718 (IN718) is manufactured and characterized in the as-manufactured condition, on account of its representative segregation and precipitation behaviours. The microstructure gradient within a build, specifically the Laves phase volume fraction evolution, is rationalized with the solidification condition and the following in-situ annealing. Precipitations of carbide/nitride/carbonitride, delta and gamma/gamma are also discussed. Hardness is measured and correlated to the Laves phase volume fraction evolution and the precipitation of gamma/gamma . The results of this study will (i) shed light on microstructure evolution during the EBM process with regard to thermal history; and (ii) deepen the current understandings of solidification metallurgy for additive manufacturing of Ni-base superalloys. (C) 2018 Elsevier Ltd. All rights reserved.

  • 26.
    Ekstrand, Gunnar
    et al.
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Asnafi, Nader
    Industrial Development Centre, Olofström, Sweden.
    On testing of the stiffness and the dent resistance of autobody panels1998Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 19, nr 4, s. 145-156Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this study has been to establish a platform which can be used in future attempts to set up at least a reasonable (scientifically based) company standard for stiffness and dent resistance tests. Stiffness and dent testing equipment was developed and used in this investigation. This equipment, which is mounted in a mechanical testing machine, consists chiefly of three parts: a table, on which the panel is placed; a fixture, which is used to restrain the panel; and a punch, with which the panel centre is loaded. Two different punches are used: a flat-headed punch of diameter 100 mm in the stiffness tests and a hemispherical punch of diameter 25 mm in the dent resistance tests. The boundary conditions play a significant role in the stiffness and the dent resistance measurements. The largest stiffness is obtained with the boundary configuration case I, whilst the boundary configuration case IV yields the smallest stiffness. The attained experimental results show that the thicker the sheet thickness at the panel centre, the greater will be the panel stiffness. The greater the panel radii (the more severe the springback), the smaller the stiffness. The experimental results show too that the larger the initial yield strength, the higher is the dent resistance. The thicker the sheet, the higher is the dent resistance. The purpose of this study has been to establish a platform which can be used in future attempts to set up at least a reasonable (scientifically based) company standard for stiffness and dent resistance tests. Stiffness and dent testing equipment was developed and used in this investigation. This equipment, which is mounted in a mechanical testing machine, consists chiefly of three parts: a table, on which the panel is placed; a fixture, which is used to restrain the panel; and a punch, with which the panel centre is loaded. Two different punches are used: a flat-headed punch of diameter 100 mm in the stiffness tests and a hemispherical punch of diameter 25 mm in the dent resistance tests. The boundary conditions play a significant role in the stiffness and the dent resistance measurements. The largest stiffness is obtained with the boundary configuration case I, whilst the boundary configuration case IV yields the smallest stiffness. The attained experimental results show that the thicker the sheet thickness at the panel centre, the greater will be the panel stiffness. The greater the panel radii (the more severe the springback), the smaller the stiffness. The experimental results show too that the larger the initial yield strength, the higher is the dent resistance. The thicker the sheet, the higher is the dent resistance.

  • 27.
    Espinoza-Cuadra, J.
    et al.
    CONACyT-México, Av. Insurgentes Sur 1582, Col. Crédito Constructor Del. Benito Juárez, C.P. 03940, Mexico, D.F., Mexico.
    Gallegos-Acevedo, P.
    Universidad Tecnológica de la Mixteca, Carretera a Acatlima Km. 2.5 Huajuapán de León, C.P. 69000, Oaxaca, Mexico.
    Mancha-Molinar, H.
    Research and Development Department, CIFUNSA, Blvd. Isidro López Z. #4003, Zona Industrial Saltillo, C.P. 25230, Coahuila, Mexico.
    Picado, Apolinar
    Natl Univ Engn UNI, Fac Chem Engn.
    Effect of Sr and solidification conditions on characteristics of intermetallic in Al–Si 319 industrial alloys2010Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 31, nr 1, s. 343-356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An experimental study was carried out to determine the effect of strontium (Sr) on the characteristic of intermetallic phases, particularly the Al5FeSi phase which present morphology of platelets or needle-like. The results showed that within the range of variables studied, the modification process caused the disappearance of the needles and only occur the precipitation of phase α (chinese script-like). Refinement of the intermetallic phases occurs in conjunction with the refinement in grain size. Both parameters depend strongly on local cooling rate (T), temperature gradient (G) and apparent rate of solidification front (V). In the case of equiaxed structures the refinement of grain size and intermetallic occurs with increasing local cooling rate and temperature gradient and decrease the apparent rate of solidification front. In the case of columnar structures, refinement of grains and intermetallic requires the increase in values of the three variables indicated. Moreover, the addition of Sr resulted in the modification of silicon eutectic, as noted in others research works.

  • 28.
    Fjellstedt, J.
    et al.
    Royal Institute of Technology, Division of Metals Casting, Stockholm, Sweden.
    Jarfors, A. E. W.
    Royal Institute of Technology, Division of Metals Casting, Stockholm, Sweden.
    El-Benawy, T.
    Royal Institute of Technology, Division of Metals Casting, Stockholm, Sweden.
    Experimental investigation and thermodynamic assessment of the Al-rich side of the Al-B system2001Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Materials & Design, ISSN 0261-3069, Vol. 22, nr 6, s. 443-449Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The phase relations in the Al-Ti-B system are of great importance for the manufacturing of Al/TiB2 composites. To describe the phase relations, the relations in the binaries Al-B, Ti-B and Al-Ti must be known. The description of the binary Al-B system has been found to be poor. The Al-rich side of the Al-B phase diagram was studied using DSC, on alloys ranging from 0.5 up to 6.4 at ·% B. The Al-rich part of the phase diagram was assessed using the experimental data and data found in the literature. The eutectic temperature was found to agree well with the literature. However, the peritectic temperature was found to be 914°C. Above the peritectic temperature a metastable primary precipitation of AlB2 below the AlB12 liquidus line was suggested. This type of degenerate peritectic reaction is similar to what has been found in Fe-based materials. This behaviour also explains the difficulty in the determination of the peritectic point by experimental means. © 2001 Elsevier Science Ltd. All rights reserved.

  • 29.
    Ganvir, Ashish
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Vassen, Robert
    Forschungszentrum Jülich GmbH, IEK-1, Jülich, Germany.
    Tailoring columnar microstructure of axial suspension plasma sprayed TBCs for superior thermal shock performance2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 144, s. 192-208Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the thermal shock behavior of thermal barrier coatings (TBCs) produced by axial suspension plasma spraying (ASPS). TBCs with different columnar microstructures were subjected to cyclic thermal shock testing in a burner rig. Failure analysis of these TBCs revealed a clear relationship between lifetime and porosity. However, tailoring the microstructure of these TBCs for enhanced durability is challenging due to their inherently wide pore size distribution (ranging from few nanometers up to few tens of micrometers). This study reveals that pores with different length scales play varying roles in influencing TBC durability. Fracture toughness shows a strong correlation with the lifetime of various ASPS TBCs and is found to be the prominent life determining factor. Based on the results, an understanding-based design philosophy for tailoring of the columnar microstructure of ASPS TBCs for enhanced durability under cyclic thermal shock loading is proposed. © 2018 The Authors

  • 30.
    Gleich, Stephan
    et al.
    Max Planck Inst Eisenforsch GmbH, Max Planck Str 1, D-40237 Dusseldorf, Germany..
    Soler, Rafael
    Max Planck Inst Eisenforsch GmbH, Max Planck Str 1, D-40237 Dusseldorf, Germany..
    Fager, Hanna
    Max Planck Inst Eisenforsch GmbH, Max Planck Str 1, D-40237 Dusseldorf, Germany.;Rhein Westfal TH Aachen, Mat Chem, Kopernikusstr 10, D-52074 Aachen, Germany..
    Bolvardi, Hamid
    Rhein Westfal TH Aachen, Mat Chem, Kopernikusstr 10, D-52074 Aachen, Germany..
    Achenbach, Jan-Ole
    Rhein Westfal TH Aachen, Mat Chem, Kopernikusstr 10, D-52074 Aachen, Germany..
    Hans, Marcus
    Rhein Westfal TH Aachen, Mat Chem, Kopernikusstr 10, D-52074 Aachen, Germany..
    Primetzhofer, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Schneider, Jochen M.
    Max Planck Inst Eisenforsch GmbH, Max Planck Str 1, D-40237 Dusseldorf, Germany.;Rhein Westfal TH Aachen, Mat Chem, Kopernikusstr 10, D-52074 Aachen, Germany..
    Dehm, Gerhard
    Max Planck Inst Eisenforsch GmbH, Max Planck Str 1, D-40237 Dusseldorf, Germany..
    Scheu, Christina
    Max Planck Inst Eisenforsch GmbH, Max Planck Str 1, D-40237 Dusseldorf, Germany.;Rhein Westfal TH Aachen, Mat Analyt, Kopernikusstr 10, D-52074 Aachen, Germany..
    Modifying the nanostructure and the mechanical properties of Mo2BC hard coatings: Influence of substrate temperature during magnetron sputtering2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 142, s. 203-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A reduction in synthesis temperature is favorable for hard coatings, which are designed for industrial applications, as manufacturing costs can be saved and technologically relevant substrate materials are often temperature-sensitive. In this study, we analyzed Mo2BC hard coatings deposited by direct current magnetron sputtering at different substrate temperatures, ranging from 380 degrees C to 630 degrees C. Transmission electron microscopy investigations revealed that a dense structure of columnar grains, which formed at a substrate temperature of 630 degrees C, continuously diminishes with decreasing substrate temperature. It almost vanishes in the coating deposited at 380 degrees C, which shows nanocrystals of similar to 1 nm in diameter embedded in an amorphous matrix. Moreover, Argon from the deposition process is incorporated in the film and its amount increases with decreasing substrate temperature. Nanoindentation experiments provided evidence that hardness and Young's modulus are modified by the nanostructure of the analyzed Mo2BC coatings. A substrate temperature rise from 380 degrees C to 630 degrees C resulted in an increase in hardness (21 GPa to 28 GPa) and Young's modulus (259 GPa to 462 GPa). We conclude that the substrate temperature determines the nanostructure and the associated changes in bond strength and stiffness and thus, influences hardness and Young's modulus of the coatings.

  • 31.
    Herrera, Martha
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sirviö, Juho A.
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Environmental friendly and sustainable gas barrier on porous materials: Nanocellulose coatings prepared using spin- and dip-coating2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 93, s. 19-25Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, environmental friendly and sustainable coatings of nanocellulose (NC) were prepared using spin- and dip-coating methods, on two different porous cellulose substrates. Microscopy studies showed that spin-coating technique was suitable for the substrate with smaller pore size, while the dip-coating was suitable for the substrate with larger pore size. The coating thickness ranged from some hundreds of nanometers for the spin-coated layers, to some micrometers for the dip-coated ones. It was also seen that the contact angle increased with the coating thickness and roughness. NC coating resulted in low oxygen permeability (between 0.12 and 24 mL ∗ μm/(m2 ∗ 24 h ∗ kPa)) at 23% RH, but at 50% RH the oxygen permeability was too high to be measured, except for the dip-coated sample with 23 μm thickness. Also, it was seen that eight month storing reduced the barrier properties of the coatings when compared with fresh materials. These results indicate that NC coatings have a great potential as sustainable alternative coating on paperboard.

  • 32.
    Hosseini, Vahid A.
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Wessman, Sten
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser. Swerea KIMAB AB, Kista, Sweden.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nitrogen loss and effects on microstructure in multipass TIG welding of a super duplex stainless steel2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 98, nr May, s. 88-97Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nitrogen loss is an important phenomenon in welding of super duplex stainless steels. In this study, a super duplex stainless steel was autogenously TIG-welded with one to four bead-on-plate passes with low or high heat inputs using pure argon shielding gas. The goal was to monitor nitrogen content and microstructure for each weld pass. Nitrogen content, measured by wavelength dispersive X-ray spectrometry, was after four passes reduced from 0.28 wt% in the base metal to 0.17 wt% and 0.10 wt% in low and high heat input samples, respectively. Nitrogen loss resulted in a more ferritic structure with larger grains and nitride precipitates. The ferrite grain width markedly increased with increasing number of passes and heat input. Ferrite content increased from 55% in base metal to 75% at low and 79% at high heat inputs after four passes. An increasing amount of nitrides were seen with increasing number of weld passes. An equation was suggested for calculation of the final nitrogen content of the weld metal as functions of initial nitrogen content and arc energy. Acceptable ferrite contents were seen for one or two passes. The recommendation is to use nitrogen in shielding gas and proper filler metals.

  • 33.
    Hosseini, Vahid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Choquet, Isabelle
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Engelberg, Dirk
    The University of Manchester, School of Materials, Manchester M13 9PL, UK.
    Roy, Matthew J.
    The University of Manchester, School of Mechanical, Aerospace and Civil Engineering,Manchester M13 9PL, UK.
    Kumara, Chamara
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    A novel arc heat treatment technique for producing graded microstructures through controlled temperature gradients2017Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 121, nr May, s. 11-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper introduces a novel arc heat treatment technique to produce samples with graded microstructures through the application of controlled temperature gradients. Steady state temperature distributions within the sample can be achieved and maintained, for times ranging from a few seconds to several hours. The technique reduces the number of samples needed to characterize the response of a material to thermal treatments, and can consequently be used as a physical simulator for materials processing. The technique is suitable for conventional heat treatment analogues, welding simulations, multi-step heat treatments, and heat treatments with controlled heating and cooling rates. To demonstrate this technique, a super duplex stainless steel was treated with a stationary TIG arc, to confirm the relationship between generated steady-state temperature fields, microstructure development, hardness, and sensitization to corrosion. Metallographic imaging and hardness mapping provided information about graded microstructures, confirming the formation of secondary phases and microstructure sensitization in the temperature range 850–950 °C. Modelling of temperature distributions and thermodynamic calculations of phase stabilities were used to simulate microstructure development and associated welding cycles.

  • 34.
    Hosseini, Vahid
    et al.
    University West, Sweden; Innovatum AB, Sweden.
    Wessman, Sten
    RISE., Swerea, KIMAB. RISE - Research Institutes of Sweden, Material och produktion, KIMAB. University West, Sweden.
    Hurtig, Kjell
    University West, Sweden.
    Karlsson, Leif
    University West, Sweden.
    Nitrogen loss and effects on microstructure in multipass TIG welding of a super duplex stainless steel2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 98, s. 88-97Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nitrogen loss is an important phenomenon in welding of super duplex stainless steels. In this study, a super duplex stainless steel was autogenously TIG-welded with one to four bead-on-plate passes with low or high heat inputs using pure argon shielding gas. The goal was to monitor nitrogen content and microstructure for each weld pass. Nitrogen content, measured by wavelength dispersive X-ray spectrometry, was after four passes reduced from 0.28 wt% in the base metal to 0.17 wt% and 0.10 wt% in low and high heat input samples, respectively. Nitrogen loss resulted in a more ferritic structure with larger grains and nitride precipitates. The ferrite grain width markedly increased with increasing number of passes and heat input. Ferrite content increased from 55% in base metal to 75% at low and 79% at high heat inputs after four passes. An increasing amount of nitrides were seen with increasing number of weld passes. An equation was suggested for calculation of the final nitrogen content of the weld metal as functions of initial nitrogen content and arc energy. Acceptable ferrite contents were seen for one or two passes. The recommendation is to use nitrogen in shielding gas and proper filler metals.

  • 35.
    Huang, Shuo
    et al.
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Li, Wei
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Li, Xiaoqing
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Schonecker, Stephan
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Bergqvist, Lars
    Royal Inst Technol, Dept Mat & Nano Phys, Electrum 229, SE-16440 Kista, Sweden..
    Holmström, Erik
    Sandvik Coromant R&D, S-12680 Stockholm, Sweden..
    Varga, Lajos Karoly
    Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Mechanism of magnetic transition in FeCrCoNi-based high entropy alloys2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 103, s. 71-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First-principles alloy theory and Monte-Carlo simulations are performed to investigate the magnetic properties of FeCrCoNiAlx high entropy alloys. Results show that face-centered-cubic (fcc) and body-centered-cubic (bcc) structures possess significantly different magnetic behaviors uncovering that the alloy's Curie temperature is controlled by the stability of the Al-induced single phase or fcc-bcc dual-phase. We show that the appearance of the bcc phase with increasing Al content brings about the observed transition from the paramagnetic state for FeCrCoNi to the ferromagnetic state for FeCrCoNiAl at room-temperature. Similar mechanism is predicted to give rise to room-temperature ferromagnetism in FeCrCoNiGa high entropy alloy.

  • 36.
    Huang, Shuo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Li, Wei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Li, Xiaoqing
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Schönecker, Stephan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Bergqvist, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Holmström, E.
    Varga, L. K.
    Vitos, Levente
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Wigner Research Centre for Physics, Hungary; Uppsala University, Sweden.
    Mechanism of magnetic transition in FeCrCoNi-based high entropy alloys2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 103, s. 71-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First-principles alloy theory and Monte-Carlo simulations are performed to investigate the magnetic properties of FeCrCoNiAlx high entropy alloys. Results show that face-centered-cubic (fcc) and body-centered-cubic (bcc) structures possess significantly different magnetic behaviors uncovering that the alloy's Curie temperature is controlled by the stability of the Al-induced single phase or fcc-bcc dual-phase. We show that the appearance of the bcc phase with increasing Al content brings about the observed transition from the paramagnetic state for FeCrCoNi to the ferromagnetic state for FeCrCoNiAl at room-temperature. Similar mechanism is predicted to give rise to room-temperature ferromagnetism in FeCrCoNiGa high entropy alloy.

  • 37.
    Islavath, Nanaji
    et al.
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India; School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046, India.
    Das, Dibakar
    School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046, India.
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Ramasamy, Easwaramoorthi
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Seed layer-assisted low temperature solution growth of 3D ZnO nanowall architecture for hybrid solar cells2017Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 116, s. 219-226Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aligned metal oxide nanostructures carry electrons efficiently, and are therefore ideal building blocks for next-generation optoelectronic devices. Herein, we report the seed-layer-assisted low-temperature solution growth of aligned 3D ZnO nanowall architecture on arbitrary substrates. By introducing a controlled amount of Al into a seed-layer, the morphology of ZnO nanostructure is gradually changed from nanowire to 3D nanowalls. Time-dependent growth experiments suggest that hydroxyl-ions present in growth solution react with Al to form Al(OH)4 which in turn binds to the positively charged Zn2 +surface and partially blocking ZnO growth along the (0001) direction and promoting lateral growth. Such aligned 3D ZnO nanowall architecture, with the unique combination of high surface-area and cage-like pores, grown on seed-layer coated transparent conductive substrate is found to be beneficial for electron transporting material (ETM) in perovskite solar cells and a maximum photocurrent density (JSC) of 7.5 mA.cm− 2 and a power conversion efficiency (η) of 2.4% are demonstrated. Our facile approach readily allows further growth of ZnO nanowires on 3D ZnO nanowall surface; thereby improving the perovskite-ZnO interface and increasing the JSC and η to 9.7 and 3.3%, respectively. This 3D ZnO nanowall-nanowire architecture opens up a novel configuration for designing high-performance optoelectronic devices.

  • 38. Jomehzadeh, E.
    et al.
    Saidi, A.R.
    Atashipour, Seyed Rasoul
    An analytical approach for stress analysis of functionally graded annular sector plates2009Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 30, nr 9, s. 3679-3685Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, an exact analytical approach is used for bending analysis of functionally graded (FG) annular sector plates. The governing equilibrium equations are obtained based on the first order shear deformation plate theory. Introducing an analytical method, the coupled governing equilibrium equations are replaced by independent equations in term of transverse deflection and a new function. Using an equivalent flexural rigidity, the solutions of FG annular sector plates can be easily extracted from equation of homogeneous annular plates. Also, it is shown that the present method can provide accurate results. Finally, the effects of power of functionally graded material (FGM), plate thickness, inner to outer radius ratio and boundary conditions on the deflection and stresses of a functionally graded annular sector plate are studied.

  • 39.
    Karimi Neghlani, Paria
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Sadeghimeresht, Esmaeil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Åkerfeldt, Pia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Luleå, 971 87, Sweden.
    Ålgårdh, Joakim
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Powder Materials & Additive Manufacturing, Swerea KIMAB AB, Kista, 164 40, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence of successive thermal cycling on microstructure evolution of EBM-manufactured alloy 718 in track-by-track and layer-by-layer design2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, s. 427-441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Successive thermal cycling (STC) during multi-track and multi-layer manufacturing of Alloy 718 using electron beam melting (EBM) process leads to a microstructure with a high degree of complexity. In the present study, a detailed microstructural study of EBM-manufactured Alloy 718 was conducted by producing samples in shapes from one single track and single wall to 3D samples with maximum 10 longitudinal tracks and 50 vertical layers. The relationship between STC, solidification microstructure, interdendritic segregation, phase precipitation (MC, δ-phase), and hardness was investigated. Cooling rates (liquid-to-solid and solid-to-solid state) was estimated by measuring primary dendrite arm spacing (PDAS) and showed an increased cooling rate at the bottom compared to the top of the multi-layer samples. Thus, microstructure gradient was identified along the build direction. Moreover, extensive formation of solidification micro-constituents including MC-type carbides, induced by micro-segregation, was observed in all the samples. The electron backscatter diffraction (EBSD) technique showed a high textured structure in 〈001〉 direction with a few grains misoriented at the surface of all samples. Finer microstructure and possibility of more γ″ phase precipitation at the bottom of the samples resulted in slightly higher (~11%) hardness values compared to top of the samples. © 2018 Elsevier Ltd

  • 40.
    Karimi, Paria
    et al.
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Sadeghi, Esmaeil
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Åkerfeldt, Pia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ålgårdh, Joakim
    Department of Engineering Science, University West, Trollhättan, Sweden. Powder Materials & Additive Manufacturing, Swerea KIMAB AB, Kista, Sweden.
    Andersson, Joel
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Influence of successive thermal cycling on microstructure evolution of EBM-manufactured alloy 718 in track-by-track and layer-by-layer design2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, s. 427-441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Successive thermal cycling (STC) during multi-track and multi-layer manufacturing of Alloy 718 using electron beam melting (EBM) process leads to a microstructure with a high degree of complexity. In the present study, a detailed microstructural study of EBM-manufactured Alloy 718 was conducted by producing samples in shapes from one single track and single wall to 3D samples with maximum 10 longitudinal tracks and 50 vertical layers. The relationship between STC, solidification microstructure, interdendritic segregation, phase precipitation (MC, δ-phase), and hardness was investigated. Cooling rates (liquid-to-solid and solid-to-solid state) was estimated by measuring primary dendrite arm spacing (PDAS) and showed an increased cooling rate at the bottom compared to the top of the multi-layer samples. Thus, microstructure gradient was identified along the build direction. Moreover, extensive formation of solidification micro-constituents including MC-type carbides, induced by micro-segregation, was observed in all the samples. The electron backscatter diffraction (EBSD) technique showed a high textured structure in 〈001〉 direction with a few grains misoriented at the surface of all samples. Finer microstructure and possibility of more γ″ phase precipitation at the bottom of the samples resulted in slightly higher (~11%) hardness values compared to top of the samples.

  • 41.
    Karimi, Paria
    et al.
    University West, Sweden.
    Sadeghi, Esmail
    University West, Sweden.
    Åkerfeldt, Pia
    Luleå University of Technology, Sweden.
    Ålgårdh, Joakim
    RISE - Research Institutes of Sweden, Material och produktion, KIMAB. University West, Sweden.
    Andersson, Joel
    University West, Sweden.
    Influence of successive thermal cycling on microstructure evolution of EBM-manufactured alloy 718 in track-by-track and layer-by-layer design2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, s. 427-441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Successive thermal cycling (STC) during multi-track and multi-layer manufacturing of Alloy 718 using electron beam melting (EBM) process leads to a microstructure with a high degree of complexity. In the present study, a detailed microstructural study of EBM-manufactured Alloy 718 was conducted by producing samples in shapes from one single track and single wall to 3D samples with maximum 10 longitudinal tracks and 50 vertical layers. The relationship between STC, solidification microstructure, interdendritic segregation, phase precipitation (MC, δ-phase), and hardness was investigated. Cooling rates (liquid-to-solid and solid-to-solid state) was estimated by measuring primary dendrite arm spacing (PDAS) and showed an increased cooling rate at the bottom compared to the top of the multi-layer samples. Thus, microstructure gradient was identified along the build direction. Moreover, extensive formation of solidification micro-constituents including MC-type carbides, induced by micro-segregation, was observed in all the samples. The electron backscatter diffraction (EBSD) technique showed a high textured structure in 〈001〉 direction with a few grains misoriented at the surface of all samples. Finer microstructure and possibility of more γ″ phase precipitation at the bottom of the samples resulted in slightly higher (~11%) hardness values compared to top of the samples.

  • 42.
    Kisielewicz, Agnieszka
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Sadeghi, Esmaeil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Sikström, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Palumbo, Gianfranco
    CNR-IFN Institute for Photonics and Nanotechnologies, Physics Department, Bari, Italy.
    Ancona, Antonio
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). CNR-IFN Institute for Photonics and Nanotechnologies, Physics Department, Bari, Italy.
    In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 7182020Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 186, artikel-id 108317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.

  • 43.
    Larker, Rickard
    et al.
    Luleå tekniska universitet.
    Anevik, K.
    Kristiansson, S.
    Loberg, Bengt
    Heat treatments of the low-expansion superalloy incoloy 909 for application in ceramic/metal joints and in metal matrix composites1992Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 13, nr 1, s. 11-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Increasing efficiency demands on gas turbines have promoted the development of superalloys with low thermal expansion up to intermediate temperatures, to reduce the need of cooling for preservation of efficient clearances between rotating and stationary parts. These materials are also of prime interest for joins to engineering ceramics such as silicon nitride and silicon carbide, and as a matrix with W or SiC fibres in metal matrix composites (MMC). The paper deals with the thermomechanical and microstructural stability of Incology 909 during possible joining and densification treatments. Thermal expansion behaviour and joining/densification temperatures suitable for retaining the desired structure of the superalloy are presented.

  • 44.
    Larsson, Per-Lennart
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Blanchard, Pierre
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    On the invariance of hardness at sharp indention of materials with general biaxial residual stress fields2013Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 52, s. 602-608Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In recent years, the influence from residual surface stresses on the global indentation properties, i.e. hardness and size of the contact area, have been studied quite frequently. The investigations presented have been based on experimental, theoretical and numerical methods and for one thing, the invariance of hardness in the case of residual equi-biaxial surface stresses, has been well-established. In the more general case, when the principal surface stresses are not necessarily equi-biaxial, corresponding results are more scattered and it is therefore the aim of the present study to remedy this shortcoming. In doing so, the problem is presently attacked using numerical methods and in particular the finite element method (FEM) is relied upon. Classical Mises elastoplastic material behavior is assumed throughout the investigation which is restricted, for clarity but not for necessity, to sharp cone indentation. The results confirm the invariance of hardness also for general stress fields when the deformation in the contact region is dominated by plastic deformation.

  • 45.
    Li, Xiaojie
    et al.
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Electron & Ion Beams, Dalian 116024, Peoples R China.;KTH Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Li, Xiaoqing
    KTH Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Schonecker, Stephan
    KTH Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Li, Ruihuan
    Changzhou Vocat Inst Mechatron Technol, Inst Mold Technol, Changzhou 213164, Peoples R China..
    Zhao, Jijun
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Electron & Ion Beams, Dalian 116024, Peoples R China..
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. KTH Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.;Res Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Understanding the mechanical properties of reduced activation steels2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 146, s. 260-272Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reduced activation ferritic/martensitic (RAFM) steels are structural materials with potential application in Generation-IV fission and fusion reactors. We use density-functional theory to scrutinize the micro-mechanical properties of the main alloy phases of three RAFM steels based on the body-centered cubic FeCrWVMn solid solution. We assess the lattice parameters and elastic properties of ferromagnetic alpha-Fe and Fe91Cr9, which are the main building blocks of the RAFM steels, and present a detailed analysis of the calculated alloying effects of V, Cr, Mn, and W on the mechanical properties of Fe91Cr9. The composition dependence of the elastic parameters is decomposed into electronic and volumetric contributions and studied for alloying levels that cover the typical intervals in RAFM steels. A linear superposition of the individual solute effects on the properties of Fe91Cr9 is shown to provide an excellent approximation for the ab initio values obtained for the RAFM steels. The intrinsic ductility is evaluated through Rice's phenomenological theory using the surface and unstable stacking fault energies, and the predictions are contrasted with those obtained by empirical criteria. Alloying with V or W is found to enhance the ductility, whereas additional Cr or Mn turns the RAFM base alloys more brittle.

  • 46.
    Li, Xiaojie
    et al.
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Electron & Ion Beams, Dalian 116024, Peoples R China.;KTH Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Li, Xiaoqing
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Schönecker, Stephan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Li, Ruihuan
    Changzhou Vocat Inst Mechatron Technol, Inst Mold Technol, Changzhou 213164, Peoples R China..
    Zhao, Jijun
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Electron & Ion Beams, Dalian 116024, Peoples R China..
    Vitos, Levente
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Uppsala Univ, Div Mat Theory, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Res Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Understanding the mechanical properties of reduced activation steels2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 146, s. 260-272Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reduced activation ferritic/martensitic (RAFM) steels are structural materials with potential application in Generation-IV fission and fusion reactors. We use density-functional theory to scrutinize the micro-mechanical properties of the main alloy phases of three RAFM steels based on the body-centered cubic FeCrWVMn solid solution. We assess the lattice parameters and elastic properties of ferromagnetic alpha-Fe and Fe91Cr9, which are the main building blocks of the RAFM steels, and present a detailed analysis of the calculated alloying effects of V, Cr, Mn, and W on the mechanical properties of Fe91Cr9. The composition dependence of the elastic parameters is decomposed into electronic and volumetric contributions and studied for alloying levels that cover the typical intervals in RAFM steels. A linear superposition of the individual solute effects on the properties of Fe91Cr9 is shown to provide an excellent approximation for the ab initio values obtained for the RAFM steels. The intrinsic ductility is evaluated through Rice's phenomenological theory using the surface and unstable stacking fault energies, and the predictions are contrasted with those obtained by empirical criteria. Alloying with V or W is found to enhance the ductility, whereas additional Cr or Mn turns the RAFM base alloys more brittle.

  • 47.
    Lindberg, S.
    et al.
    RISE, Innventia.
    Roos, A.
    Kihlstedt, A.
    RISE, Innventia.
    Lindström, M.
    RISE, Innventia.
    A product semantic study of the influence of the sense of touch on the evaluation of wood-based materials2013Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, s. 300-307Artikel i tidskrift (Refereegranskat)
  • 48.
    Linvill, Eric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.). KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Larsson, Per A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Östlund, Sören
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.). KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Advanced three-dimensional paper structures: Mechanical characterization and forming of sheets made from modified cellulose fibers2017Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 128, s. 231-240Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose partially converted to dialcohol cellulose has been identified as a potential breakthrough material for the production of bio-based, complex, double-curved surfaces due to its extensive strain-at-break characteristics (reaching as great as 80% in tensile loading). Tensile testing of handsheets made from modified cellulose fibers was conducted from 50 to 90% relative humidity (RH) and from 23 to 150 °C. Strain-at-break of the handsheets ranged from 35 to 80% over this humidity and temperature range, which is significantly greater than typical cellulose-based materials. The combined effect of moisture and temperature was further investigated by dynamic mechanical thermal analysis, which was utilized to determine the glass-transition temperature of the handsheets as a function of relative humidity. Based on the tensile test results and verified by the three-dimensional (3-D) forming and simulation, a forming limit diagram (strain-based failure surface which describes and illustrates the formability of the material) for the handsheets was generated. This forming limit illustrates significant extent to which this bio-based material can be 3-D formed into advanced structures. Furthermore, temperature was identified as the best, quickest, and most controllable method of improving extensibility of this material during 3-D forming.

  • 49.
    Liu, Hailong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymerteknologi. KTH, Skolan för teknikvetenskap (SCI), Teknisk mekanik, Farkostteknik och Solidmekanik, Hållfasthetslära.
    Ahlinder, Astrid
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymerteknologi.
    Yassin, M. A.
    Finne Wistrand, Anna
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymerteknologi.
    Gasser, T. Christian
    KTH, Skolan för teknikvetenskap (SCI), Teknisk mekanik, Farkostteknik och Solidmekanik, Hållfasthetslära.
    Computational and experimental characterization of 3D-printed PCL structures toward the design of soft biological tissue scaffolds2020Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 188, artikel-id 108488Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Degradable porous polymeric structures are attractive candidates for biological tissue scaffolds, and adequate mechanical, transport, chemical and biological properties determine their functionality. Aside from the properties of polymer-based materials, the scaffold's meso-structure controls its elasticity at the organ length-scale. This study investigated the effect of the meso-structure on scaffolds' mechanical and transport properties using finite element analysis (FEA) and computational fluid dynamics (CFD). A number of poly (ε-caprolactone) (PCL) - based scaffolds were 3D printed, analyzed by microcomputed tomography (micro-CT) and mechanically tested. We found that the gradient (G) and gradient and staggered (GS) meso-structure designs led to a higher scaffold permeability, a more homogeneous flow inside the scaffold, and a lower wall shear stress (WSS) in comparison with the basic (B) meso-structure design. The GS design resulted in scaffold stiffness as low as 1.07/0.97 MPa under compression/tension, figures that are comparative with several soft tissues. Image processing of micro-CT data demonstrated that the imposed meso-structures could have been adequately realized through 3D printing, and experimental testing validated FEA analysis. Our results suggest that the properties of 3D-printed PCL-based scaffolds can be tuned via meso-structures toward soft tissue engineering applications. The biological function of designed scaffolds should be further explored in-situ studies.

  • 50. Liu, Xihe
    et al.
    Zhao, Congcong
    Zhou, Xin
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Tsinghua University, China.
    Liu, Wei
    Microstructure of selective laser melted AlSi10Mg alloy2019Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 168, artikel-id 107677Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of laser power during selective laser melting (SLM) on the grain morphology and texture component in AlSi10Mg alloy has been investigated, using electron backscattered diffraction (EBSD). Both equiaxed and columnar grainswere observed. The formation of equiaxed grainswas attributed to the huge thermal gradient on the border of melt pool and the columnar to equiaxed transition (CET) occurred in front of the columnar grains. The grain size of lowlaser power samplewas found smaller than that of higher ones. A fine pseudoeutectic structure, in which Si existed as fibrous, was observed because of the high cooling rate. This paper, from a new angle, explained the formations of three different zones across the melt pool, which were differentiated by the morphology of Si phase. The three zones correspond to the three temperature zones, whichwere divided by liquidus and solidus temperature, during the heating by laser beam. The coarse zones are formed by reheating the basic metal to semi-solid state when the temperature is lower than the liquidus temperature but higher than the solidus temperature.

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