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  • 251.
    Barrirero, Jenifer
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Saarland Univ, Germany.
    Pauly, C.
    Saarland Univ, Germany.
    Engstler, M.
    Saarland Univ, Germany.
    Ghanbaja, J.
    Univ Lorraine, France.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Li, J.
    Univ Leoben, Austria.
    Schumacher, P.
    Univ Leoben, Austria.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Muecklich, F.
    Saarland Univ, Germany.
    Eutectic modification by ternary compound cluster formation in Al-Si alloys2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 5506Article in journal (Refereed)
    Abstract [en]

    Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are studied and their influence on the microstructure is compared to further understand this modification. The two elements impact the alloy differently, where Eu modifies Si into a coral-like structure while Yb does not. Atom probe tomography shows that Eu is present within the Si phase in the form of ternary compound Al2Si2Eu clusters, while Yb is absent in the Si phase. This indicates that the presence of ternary compound clusters within Si is a necessary condition for the formation of a coral-like structure. A crystallographic orientation relationship between Si and the Al2Si2Eu phase was found, where the following plane normals are parallel: 011(Si) //0001(Al2Si2Eu), 111(Si)//6 (7) over bar 10(Al2Si2Eu) and 011(Si)//6 (7) over bar 10(Al2Si2Eu). No crystallographic relationship was found between Si and Al2Si2Yb. The heterogeneous formation of coherent Al2Si2Eu clusters inside the Si-phase is suggested to trigger the modification of the microstructure.

  • 252.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Numerical Analysis and Measurement of Residual Stresses in Multi Pass Welding - Influence on Fatigue Root Crack Propagation2006In: TRENDS IN WELDING RESEARCH, PROCEEDINGS / [ed] David SA; DebRoy T; Lippold JC; Smartt HB; Vitek JM, MATERIALS PARK: ASM INTERNATIONAL , 2006, p. 589-594Conference paper (Refereed)
    Abstract [en]

    The purpose of this study is to investigate the residual stresses near the weld root and the weld toe for multi-pass welded tube-to-plates, and the influence of residual stresses on multiaxial fatigue of tubular joints. Two different tubular joint configurations were studied; a three-pass single-U weld groove for maximum weld penetration and a two-pass fillet (no groove) welded tube-to-plates for minimum weld penetration. An axi-symmetric finite element model was developed to calculate the temperature distribution, HAZ, penetration depth and the residual stress distribution for the sequentially coupled thermo-mechanical analysis. The calculated geometry and the temperature distribution of the fusion zone showed good agreement with the micro samples of the welds. The calculated residual stresses was compared with experimental results and showed qualitatively good agreement. The "design root crack" is under compressive stresses in both configuration, -230 MPa for the single-U weld groove and -120 MPa for the fillet weld, respectively. Also the weld toe, transition between weld and tube, is under compressive stresses. Multi-axial fatigue tests were performed in order to study weld root crack propagation. The tube structures were loaded with a static internal pressure in order to separate the design root crack and initiate the crack growth. The fatigue tests show that, depending on the size of the static imposed internal pressure, different crack paths are received.

  • 253.
    Barsoum, Zuheir
    et al.
    KTH. Nordic Welding Engineering AB, Nansta 208, Forsa, Sweden.
    Stenberg, Thomas
    KTH. Nordic Welding Engineering AB, Nansta 208, Forsa, Sweden.
    Lindgren, E.
    Fatigue properties of cut and welded high strength steels-Quality aspects in design and production2018In: Procedia Engineering, Elsevier, 2018, Vol. 213, p. 470-476Conference paper (Refereed)
    Abstract [en]

    In this study, several aspects regarding effect of quality on the fatigue strength in welded cut HSS have been investigated and are discussed. A novel numerical algorithm has been developed which assesses the welded surface and calculates and quantifies weld quality parameters and the presence of defects which are critical in fatigue applications. The algorithm is designed for implementation in serial production. It will provide robust and reliable feedback on the quality being produced, which is essential if high strength steels are utilized and high quality welds are necessary for the structural integrity of the welded component. Two welding procedures which can increase the weld quality in as welded conditions have been assessed. It was found that by using these methods, the fatigue strength can be increased with 20% compared to normal weld quality. Furthermore, two fatigue assessment methods ability to account for increased weld quality in low cycle and high cycle fatigue applications has been studied. One of these methods showed sufficient accuracy in predicting the fatigue strength with small scatter and also account for increased weld quality. The influence of surface quality on cut edges was studied and the fatigue strength was estimated using international standards and a fatigue strength model for cut edges. It was found that the fatigue strength in testing was 15-70% higher compared to the estimation, thus proving a weak link between the international standard and fatigue strength.

  • 254.
    Basirat, Mitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    An Insight into the Effect of Deformation on Carbide Dissolution in the Band Structure of Bearing Steel2013In: Diffusion In Solids And Liquids VIII, Trans Tech Publications Inc., 2013, p. 171-176Conference paper (Refereed)
    Abstract [en]

    Dendritic segregation in deformed samples remains in the form of band structure, which is a high-strained region. The present work investigates the effect of the uphill diffusion process, occurring during deformation, on the dissolution of carbide particles in the band structure. A series of hot compression tests are performed on the cast structure of bearing steel by using a hydraulic testing machine, MTS 810. Cylindrical specimens are deformed in a temperature range of 800 degrees C to 900 degrees C and at strain rates of 5s(-1) and 0.5s(-1). In order to eliminate the recovery process, samples are immediately quenched after the compression. The microsegregation of Cr, Mo, Mn and Si are investigated in the band structure, which shows a tendency of uphill diffusion during deformation process. The results show that the volume fraction of carbides varies with the increased straining. The results also show that deformation causes the fragmentation, dispersion of pearlite in the dendrites and the dissolution of spheroidized carbides in the band structure.

  • 255.
    Basirat, Mitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Disorder Structure formation during plastic defroamtion of pure copper2012In: International journal of material science, ISSN 0973-4589, Vol. 7, no 3, p. 169-182Article in journal (Refereed)
    Abstract [en]

    The effect of the deformation process at 300˚C on the cast structure of pure copper is investigated. The temperature measurements during compression test are performed by a new experimental method developed earlier [1]. The deformed structure is studied with the aid of optical and transmission electron microscopy. Micrographs show the formation of deformed bands with high internal energy, due to many lattice defects. The strain energy calculations are based on an energy balance and the data obtain from micrograph studies performed by optical and transmission electron microscopy. It is found that there is a significant difference in the strain energy values obtained in the present work compared to the values available in the literature.  The strain energy values obtained in the band structure of the present work are 17.4% to 24% of the heat of fusion of Cu. Such high energy is sufficient to change the normal FCC structure to a disordered atomic structure in the highly deformed regions, during plastic deformation.

  • 256.
    Basirat, Mitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Effect of deformation on microsegregation in cast structure of bearing steel2012In: TMS 2012 141st Annual Meeting & Exhibition - Supplemental Proceedings, Vol 2: Materials Properties, Characterization, And Modeling, 2012, Vol. 2, p. 309-316Conference paper (Refereed)
    Abstract [en]

    Microsegregation changes in the cast structure of a five-ton ingot of ball bearing steel are investigated by a series of hot compression tests. Cylindrical specimens are deformed at a temperature range of 800 degrees C to 900 degrees C and strain rates of 0.5 s(-1). Samples are quenched after the compression in order to eliminate the homogenization time. Subsequently they are analysed with the aid of Electron Microprobe Analysis (EMPA) in order to investigate the effect of hot compression on microsegregation of Mo, Cr, Mn and Si. It is found that highly segregated regions are regions for formation of deformation bands. It seems that the degree of microsegregation increases by increasing the deformation. An attempt is made to estimate the diffusion coefficients of alloying elements during the deformation process. The increase of microsegregation during deformation is explained by tendency for uphill diffusion.

  • 257.
    Basirat, Mitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Plastic Deformation and Recrystallization in Incoloy 825Manuscript (preprint) (Other academic)
  • 258.
    Basu, Somnath
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Studies on dephosphorisation during steelmaking2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This work is aimed at understanding the thermodynamic principles influencing the phosphorus partition between slag and steel during steelmaking, particularly during refining of high-phosphorus hot metal using the basic oxygen steelmaking (BOS) process. Mapping of the slag path has been carried out using a mass balance model based on input conditions and off-gas analysis, which has been validated by intermediate measurements of slag and metal composition in an industrial basic oxygen furnace (BOF). The slag composition is found to vary over a wide range of basicity (%CaO/%SiO2) and iron oxide content. The partition of phosphorus increases with progress of refining but reduces during the intermediate period, corresponding to a decrease in iron oxide concentration and formation of “dry slag”. The phosphorus partition ratio increases again towards the end of the process. The equilibrium partition ratios for such conditions have been theoretically estimated using slag “model(s)”, based on the estimated slag compositions. It is seen that the partition ratio of phosphorus remains within 45% – 60% of the equilibrium value, showing a gradual decrease with progress of the refining process.

    Equilibrium phosphorus partition ratios for slags containing low concentrations of MnO and Al2O3 have been experimentally determined, over the ranges of basicity and iron oxide concentration approximately corresponding to that observed in the typical BOS process. It is seen that the equilibrium phosphorus partition ratio is practically independent of basicity greater than 2.5 – 2.6, over the entire range of temperature and FeOx concentration studied. Variation of the activity of P2O5 with basicity and FeOx concentration has been investigated to explain the trends observed in the variation of phosphorus partition ratio. It is seen that the activity coefficient of P2O5 is lowest, and hence most conducive for removal of phosphorus from steel, over certain finite ranges of basicity and iron oxide concentration. It follows that the efficiency of dephosphorisation is likely to be maximum if the basic oxygen steelmaking process is operated within these ranges. Simultaneous with this work, mathematical correlations have been developed for estimation of P2O5 activity coefficient and phosphorus partition ratio as functions of slag composition. The correlations are compared with those proposed by earlier workers and are found to result in better predictions over certain composition ranges.

  • 259.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    A model for activity coefficient of P2O5 in BOF slag and phosphorus distribution between liquid steel and slag2007In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 8, p. 1236-1238Article in journal (Refereed)
  • 260.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Phosphorus partition between liquid steel and CaO-SiO2-FeOx-P2O5-MgO slag containing 15-25 %FeO2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 4, p. 623-630Article in journal (Refereed)
    Abstract [en]

    CaO-SiO2-FeO2-P2O5-MgO bearing slags are typically used in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influence of factors such as FeO content and basicity on the phosphorus partition ratio was investigated at two different temperatures. The partition ratio initially increased with basicity but remained constant beyond a basicity of 2.5 to 2.6. An increase in the FeO content up to 18 to 20 mass pct was beneficial for the phosphorus partition at a basicity level of 2 to 3, but a higher concentration of FeO resulted in a decrease in the phosphorus partition ratio; the FeO concentration corresponding to this transition varied with basicity and temperature. At even lower basicities, however, the equilibrium phosphorus partition showed either no change, or a marginally decreasing trend, with an increase in the FeO content.

  • 261.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    KTH.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Phosphorus partition between liquid steel and CaO-SiO2-P2O5-MgO slag containing low FeO2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 3, p. 357-366Article in journal (Refereed)
    Abstract [en]

    CaO-SiO2-FeOx-P2O5-MgO bearing slags are typical in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influences of FeO concentration and basicity on the equilibrium phosphorus partition ratios were experimentally determined at temperatures of 1873 and 1923 K, for conditions of MgO saturation. The partition ratio initially increased with basicity but attained a constant value beyond basicity of 2.5. An increase in FeO concentration up to approximately 13 to 14 mass pet was beneficial for phosphorus partition.

  • 262.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    KTH.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Halder, Jayanta
    Change in phosphorus partition during blowing in a commercial BOF2007In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 5, p. 766-768Article in journal (Refereed)
  • 263.
    Bauer, Tobias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Andersson, Joel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. LKAB, Malmberget.
    Sarlus, Zimer
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Lund, Cecilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Kearney, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Structural controls on the setting, shape and hydrothermal alteration of the Malmberget IOA deposit, northern Sweden2018In: Economic geology and the bulletin of the Society of Economic Geologists, ISSN 0361-0128, E-ISSN 1554-0774, Vol. 113, no 2, p. 377-395Article in journal (Refereed)
    Abstract [en]

    The Malmberget iron oxide-apatite (IOA) deposit in northern Sweden is one of the largest underground iron ore mine operations in the world with estimated ore reserves in 2015 of 346 million metric tons (Mt) at 42.5% Fe. The underground operation is concentrated in 10 orebodies of 5 to 245 Mt each, which currently produce 17.4 Mt of apatite iron ore per year. Structural investigations were combined with data on hydrothermal mineral assemblages in order to reconstruct the relative timing of ore-forming, deformation, and overprinting hydrothermal events. The results improve the understanding of structural geometries, relationships, and control on orebody transposition in the deposit. A first compressional event (D1) around 1.88 Ga represents the main metamorphic event (M1) in the area and was responsible for a strong transposition of potential primary layering and the orebodies and led to the formation of a composite S0/1 fabric. A subsequent F2 folding event around 1.80 Ga resulted in the formation of an open, slightly asymmetric synform with a steeper southeast limb and a roughly SW-plunging fold axis. The result of structural modeling implies that the ore formed at two separate horizons. The folding was accompanied by stretching, resulting in boudinage of the iron orebodies. D2-related high-strain zones and syntectonic granites triggered the remobilization of amphibole, biotite, magnetite, and hematite and controlled the formation of iron oxide-copper-gold (IOCG)-type hydrothermal alteration, including an extensive K-feldspar alteration accompanied with sulfides, scapolite, and epidote. This shows a distinct time gap of at least 80 m.y. between the formation of iron oxides and sulfides. Brittle structures and the lack of an axial planar parallel fabric in conjunction with previous results suggest upper crustal, low-pressure, and high-temperature conditions during this D2 deformation phase, indicating a hydrothermal event rather than a purely regional metamorphic compression. It is proposed in the present study that the Malmberget IOA deposit was deformed and metamorphosed during a 1.88 Ga crustal shortening event. Moreover, the Malmberget IOA deposit was affected by a 1.8 Ga folding and hydrothermal event that is related to a regional IOCG overprint.

  • 264.
    Baykov, Vitaly
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jerlerud Perez, Rosa
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sundman, Bo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Structural stability of intermetallic phases in the Zr-Sn system2006In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 55, no 5, p. 485-488Article in journal (Refereed)
    Abstract [en]

    A thermodynamic description of the intermetallic compounds in the Zr-Sn binary system has been obtained using total energy calculations by means of the Vienna ab initio simulation package. Our calculations show that hexagonal compounds Zr5Sn4 and Zr5Sn3 are the most stable phases in the Zr-Sn binary system. Their high stability is found to be due to hybridization of the Sn 5p with Zr 4d electronic states. Based on the calculated energies, the conclusion is made that Zr substitution on the Sri sites takes place in the Zr4Sn phase, which accounts for the unusual stoichiometry of this Cr3Si structure type compound.

  • 265.
    Beattie, D.A.
    et al.
    Ian Wark Research Institute, University of South Australia.
    Lidström-Larsson, Margareta
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    In situ total internal reflection Raman spectroscopy of surfactant adsorption at a mineral surface2006In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 41, no 2, p. 198-204Article in journal (Refereed)
    Abstract [en]

    We present the first attempt to characterise surfactant adsorption from solution onto a particle film using total internal reflection Raman spectroscopy. Three surfactant collectors of interest to the mineral processing industry were studied in their adsorption onto sphalerite: heptyl xanthate, 2-mercaptobenzothiazole (MBT), and O,O-dibutyldithiophosphate (DTP). All three surfactants adsorbed to the surface of the sphalerite. Adsorption of heptyl xanthate was monitored as a function of time and increasing concentration. The spectrum of heptyl xanthate indicated the presence of a small amount of dixanthogen on the surface of the sphalerite. MBT adsorption studies were complicated due to the fluorescence of the adsorbed layer. However, peaks due to the adsorbed MBT were observed on top of the fluorescent background, allowing the identification of the adsorbed species to be confirmed as the oxidised dimer species. Spectra obtained from MBT and DTP co-adsorption studies did not display the strong adsorbate layer fluorescence, indicating that the fluorescence spectrum of the adsorbed MBT is most likely affected by ring-ring interactions.

  • 266.
    Beaussant Törne, Karin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Investigation of corrosion properties of metals for degradable implant applications2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Degradable metallic implants are a new class of biomaterials with potentialto replace permanent materials in temporary applications to reduce therisk of long term adverse effects.This thesis focuses on in vitro testing of zinc and magnesium based metals.As new degradable metals are developed screening of new materials within vitro test methods is an attractive option to avoid unnecessary, time consumingand expensive animal studies. The influence of factors such as ioniccomposition of the test solution, buffer system, strain and alloy compositionwas investigated. By employing electrochemical in situ techniques such asimpedance spectroscopy it is possible to study the metal-solution interfaceand determine the properties of the corroding surface. Ex situ surface characterizationtechniques such as scanning electron microscopy and infraredspectroscopy were then used to complement the results of the electrochemicalmeasurements.The importance of appropriate selection of the test solution is highlightedin this work. Zinc was found to corrode in Ringer’s solution by a mechanismcloser to in vivo corrosion than in a phosphate buffered saline solution(PBS).Ringer’s solution is therefore the more appropriate test environment for longterm evaluation of zinc based metals.When evaluating the corrosion of Zn-Mg and Zn-Ag alloys in Ringer’ssolution selective dissolution was found to occur for both types of alloys. Localprecipitation and formation of a porous, less protective, layer of corrosionproducts was found for Zn-Mg alloys. The selective dissolution of Zn-Agalloy caused an enrichment of AgZn3 on the surface which may affect thebiocompatibility of the alloy.The use of HEPES to maintain the pH of the test solution increasedthe corrosion rate of magnesium due to formation of a less protective layerof corrosion products. Magnesium corrosion should therefore preferably bestudied in solutions where the pH is maintained by the biological buffer systemCO2/H2CO3.In addition to saline solutions human whole blood and plasma were evaluatedas more clinically relevant in vitro environments. They were found toproduce reproducible results and to be suitable for short term experiments.Formation of a corrosion product layer comprised of both organic and inorganicmaterial was detected on zinc in both plasma and whole blood.During anodic polarization the adsorption of organic species on the zincsurface was found to increase the surface coverage of Zn ions in whole blood.The increased surface coverage then allowed for precipitation of a protectivelayer of Zn5(PO4)3 and a subsequent decrease in corrosion rate at higherpotentials.When subjecting zinc samples to strain the organic/inorganic corrosionproduct formed in whole blood was observed by impedance spectroscopy toprevent micro cracking and premature failure.The cracking of magnesium alloy samples under applied strain was alsocharacterized by impedance. Changes in surface properties due to crack initiation

  • 267.
    Beck, Chloé
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Influence of composition and production route on the miscrostructure and precision of cemented carbide products2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis focused on the precision of hardmetal rods after diamond coating, mimicked by annealing. The aim of this study was to determine the importance of the effect of Cobalt (Co) on the lack of precision of the rods, but as a start the process reliability has been tested.

    Rods made with the same batch number but with different production numbers have been analyzed and compared by measuring and comparing their mean intercept length and contiguity.

    After study, the parameters did not show any consequential changes for the three production numbers. It was then concluded that the production route was stable.

    As for the Co-line, four formulations (one non doped, two with various amounts of Chromium (Cr) and one Vanadium (V) doped) were sintered with different conditions (four H2 pre-treatment temperatures (800 °C to 1100 °C) and Hot Isostatic Pressing (HIP) for half of them) in order to influence the Carbon (C) balance of the samples.

    This second section showed a certain influence of the type of doping. When compared to non-doped samples, V tend to worsen the precision of the rods while Cr had contradictory results: when added in small amounts (0.05 wt%) it worsened the runout whereas it improved it when added in larger amounts (0.5 wt%). It is possible that some non-representative false results happened in this section. Nevertheless, it is certain that Cr have an impact on the binder state.

    HIP treatment improved the final distortion of the rods compared to non-HIP ones. The found explanation is that the grains were subjected to rearrangement during HIP treatment and thus were less likely to move during annealing. In addition, the amount of W dissolved into Co was measured and indicated a change in the binder composition between non-HIP and HIP samples.

     The H2 pre-treatment temperature also had an impact on the precision as it induced several different positions in the carbon window of the products.

  • 268.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Nothern Research Institute Narvik, Norway.
    Moosberg-Bustnes, J.
    Kennedy, M. W.
    Aune, R. E.
    Reduction of commercial hematite pellet in isothermal fixed bed-experiments and numerical modelling2016In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 43, no 1, p. 31-38Article in journal (Refereed)
    Abstract [en]

    In the present work, fixed bed reduction experiments were conducted at 1173 K over a range of H-2/CO ratios from 0.8 to 2.0 and subsequently modelled numerically (R). The model consists of two one-dimensional, isothermal and time dependent models. The gas-solid reactions were kinetically modelled using a modified shrinking core approach, and the equations were solved using the commercial software COMSOL Multiphysics H. The simulation results agree with thermal gravity experimental data with an average difference of 2.5%. A sensitivity analysis was conducted using the numerical model to establish the optimum operational conditions. The effects of the reducing gas ratio and flow rate, pellet radius and porosity, and the total bed height on the overall degree of reduction were also investigated.

  • 269.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Northern Research Institute Narvik, Norway.
    Moosberg-Bustnes, John
    Kennedy, Mark W.
    Aune, Ragnhild E.
    Reduction kinetics of commercial haematite pellet in a fixed bed at 1123-1273 K2016In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 43, no 5, p. 394-402Article in journal (Refereed)
    Abstract [en]

    In the present study a model for future use in the modelling of moving bed direct reduction reactors has been developed. The model of a fixed bed reactor for the production of sponge iron from haematite incorporates both heat-and mass-transfer, as well as the chemical reduction rate. The model results were compared to the experimental data obtained from a lab scale reactor in the temperature range 1123-1273 K, as well as to the output from a simple model assuming isothermal conditions. The H-2/CO ratio (beta) of the reducing gas was in all cases varied from 0.8 to 2.0. Overall the non-isothermal model developed permits a more accurate representation of the experimental data than the isothermal estimates, with a typical discrepancy of only 1.3%.

  • 270.
    Belov, Ilia
    et al.
    Jönköping University, Sweden.
    Payandeh, Mustafa
    Jönköping University, Sweden.
    Jarfors, Anders E. W.
    Jönköping University, Sweden.
    Leisner, Peter
    RISE - Research Institutes of Sweden. Jönköping University, Sweden.
    Wessén, Magnus
    Jönköping University, Sweden.
    Effect of fillets on heat transfer in a rheocast aluminium heatsink2016In: 2016 17th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), 2016, article id 7463320Conference paper (Refereed)
    Abstract [en]

    The effect of fillets formed between the base and plate fins of rheocast aluminium heatsinks on the thermal resistance of the heatsinks has been quantified by simulation. Simulation methodology, including sequential optimization has been developed in order to determine hotspot distributions where the fillets have the maximum effect. Combination of different fillet dimensions with various base thickness levels and aluminium alloys having inhomogeneous thermal conductivity have been investigated. For the studied cases, the effect of fillets on heatsink thermal resistance differs from negligible to 6%. The results would guide thermal designers on contribution of fillets to the heat transfer in multi-fin heatsinks for natural convection.

  • 271.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Simulering av ytbeläggning på gjutna komponenter2015In: Gjuteriet, no 8, p. 49-Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Inom forskningsområdet Ytteknik används modellering och simulering bland annat för att analysera ytbeläggningsprocesser på komplexa geometrier. Detta är ett multidisciplinärt område som täcker bl.a. elektrokemi, jontransport och Computational Fluid Dynamics (CFD) för beräkningar av strömningsfenomen. Numeriska modelleringsverktyg används i utformandet av processen för att optimera processparametrar både med avseende på ytbeläggningens struktur och förbättrad fördelning av ytbeläggningen. Genom M-ERA projektet som finansierats av VINNOVA har en modell tagits fram för att beskriva ytbeläggning av silver av ett gjutet radiofilter i en silvercyanidlösning. Med målet att ha en minsta ytbeläggningstjocklek på 1 μm har både den elektriska strömmen och ytbeläggningstiden varierats för att uppnå en jämn ytbeläggning och minska förbrukningen av silver. Med hjälp av mätningar på komponenter har man även kunnat validera modellerna.

  • 272.
    Belov, Ilja
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Jarfors, Anders E.W
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Simulering av prestandan hos rheogjutna kylflänsar2016In: Gjuteriet, ISSN 0017-0682, no 6, p. 49-Article in journal (Other academic)
  • 273.
    Beno, Thomas
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Isaksson, Marina
    Pejryd, Lars
    University West, Department of Engineering Science, Division of Production Engineering.
    Investigation of Machining Greek Ascaloy with Minimal Quantity Lubrication Sustainable/Cleaner Manufacturing2008In: LCE 2008: 15th CIRP International Conference on Life Cycle Engineering: Conference Proceedings, Sidney, 17-19 March, 2008Conference paper (Refereed)
  • 274.
    Berg, Martin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    The effect of Al2O3, CaO and SiO2 on the phase relations in vanadium containing slags2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today, the main raw material for vanadium production is vanadium containing steelmaking slags. The yield of the vanadium extraction process is affected by the composition of the slag, which in turn determines the phases present, the fractions of the phases and the distribution of the elements between the phases. The aim of this thesis was to experimentally investigate the effect of Al2O3, CaO and SiO2 on the phase relations in vanadium containing slags at 1673 K.

    Synthetic slags, in which the contents of Al2O3, CaO and SiO2 were varied individually, were equilibrated at 1673 K in a vertical resistance furnace. Closed molybdenum crucibles were used to set the oxygen potential of the individual samples.  The phases present, the phase compositions and the phase fractions of the samples were studied using SEM-EDS and LOM combined with an image analysis software.

    The results indicate that the samples consisted of a mixture of a vanadium and iron rich spinel phase and an iron and silicon rich liquid phase at 1673 K. Practically all the vanadium was concentrated into the spinel phase while no free silica or solid phases into which both calcium and vanadium concentrate to a significant extent were observed. The effect of Al2O3 on the phase compositions and the phase fractions was seen to be limited in the range studied. CaO primarily affected the composition of the liquid phases, while the effect on the phase fractions was small. SiO2 affected both the composition and fraction of the phases. The main effect was a decreased fraction of spinel phase, with an increasing vanadium content in the spinel phase as consequence.

  • 275.
    Berg, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lee, Jaewoo
    Hyundai Steel, 1480 Bukbusaneop Ro, Dangjin Si 31719, Chungnam, South Korea..
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Partitioning of Calcium Between Liquid Silver and Liquid Iron2018In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 49, no 3, p. 949-952Article in journal (Refereed)
    Abstract [en]

    The partitioning of calcium between liquid silver and liquid iron at 1823 K and 1873 K (1550 degrees C and 1600 degrees C) was studied experimentally using a closed molybdenum container. The calcium potential in the container was controlled by the composition of the alloys in equilibrium. The results agreed well with previous experimental measurements and indicated that the effect of temperature was not very pronounced in the temperature range studied.

  • 276.
    Berg, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lee, Jaewoo
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Study on the Equilibrium Between Liquid Iron and Calcium Vapor2017In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, no 3, p. 1715-1720Article in journal (Refereed)
    Abstract [en]

    The solubility of calcium in liquid iron at 1823 K and 1873 K (1550 A degrees C and 1600 A degrees C) as a function of calcium potential was studied experimentally. The measurements were performed using a closed molybdenum holder in which liquid calcium and liquid iron were held at different temperatures. The results indicate a linear relationship between the activity of calcium, relative to pure liquid calcium, and the mole fraction of dissolved calcium in liquid iron, with a negligible temperature dependency in the ranges studied. The activity coefficient of calcium in liquid iron at infinite dilution, was calculated as 1551.

  • 277.
    Bergh, Gustav
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Förslitning av fräsverktyg2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 278.
    Berglund, Gun
    Luleå tekniska universitet.
    Pulp Chemistry in Sulphide Mineral Flotation1991In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 33, no 1-4, p. 21-31Article in journal (Refereed)
    Abstract [en]

    Variations in the oxidizing conditions of the pulp and their subsequent effects on flotation were examined for three types of natural sulphide ore, a complex pyrite ore, a sphalerite-galena ore and a chalcopyrite ore. Different gas mixtures ranging from pure nitrogen to pure oxygen were used to control the oxidizing conditions. The use of an oxygen rich flotation gas was found to be a suitable method for changing the oxidizing conditions and improving flotation under controlled conditions. The flotation results were correlated to the oxygen content and the redox potential, parameters which describe the pulp chemistry conditions.

  • 279.
    Berglund, Gun
    Luleå tekniska universitet.
    Pulpkemiska mätningar vis sulfidmineralflotation1986In: Workshop i mineralteknik: Luleå 11-12 februari 1986 / [ed] Börje Sköld; Eric Forssberg, MinFo , 1986, p. 123-141Conference paper (Other academic)
  • 280.
    Berglund, Gun
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of different gases in flotation of sulphide minerals1989In: Advances in Coal and Mineral Processing Using Flotation: Proceedings of an Engineering Foundation Conference / [ed] Subhash Chander; Richard R. Klimpel, Littleton, Colo: Society for Mining, Metalurgy and Exploration, 1989, p. 71-76Conference paper (Refereed)
    Abstract [en]

    Sulfide mineral flotation is known to be affected by oxidation-reduction conditions in the pulp, although there is some doubt as to whether it is the oxidizing environment or the type of oxidant which influences flotation. Variations in the oxidizing conditions of the pulp and their subsequent effect on flotation were examined for two types of natural sulphide ore, a galena-sphalerite ore and a complex pyrite ore. Different gas mixtures ranging from pure nitrogen to pure oxygen were used to control the oxidizing conditions. Zinc recovery increased with a more oxidizing environment, and nitrogen gas acted almost as a depressant for sphalerite in the flotation of the Pb-Zn ore. For the complex pyrite ore, the selectivity between chalcopyrite and both gangue and pyrite improved when the environment was oxidizing, resulting in higher Cu recovery in the copper rougher concentrate.

  • 281. Berglund, Gun
    et al.
    Pålsson, Bertil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Praktisk och teoretisk utvärdering av minipilotförsök på Laisvallmalm1989In: Konferens i mineralteknik: Luleå 14-16 februari 1989 / [ed] Börje Sköld; Eric Forssberg, MinFo , 1989, p. 97-109Conference paper (Other academic)
  • 282.
    Berglund, Johan
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Kjellberg, Mikael
    Liljengren, Magnus
    Kjellsson, Kenneth
    New Test Method for Detection and Analysis of Burrs and Slivers in Trimming and Punching Aluminium Sheet Metal2014Conference paper (Refereed)
  • 283.
    Berglund, Johan
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Troell, Eva
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Surface Topography of Nitrided Steel Surfaces2017Conference paper (Other academic)
  • 284. Bergman, A
    et al.
    Jarfors, Anders
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Liu, Zhen
    Fredriksson, Hasse
    Insitu fomation of carbide composites by liquid-solid reactions1992In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 79/80, p. 213-234Article in journal (Refereed)
  • 285.
    Bergman, Dan
    Luleå tekniska universitet.
    Program för beräkning av siktkurvor1986In: Datorer inom mineraltekniken: Luleå 20-21 november 1985 / [ed] Börje Sköld; Eric Forssberg, MinFo , 1986, p. 85-93Conference paper (Other academic)
  • 286.
    Bergman, Dan
    et al.
    Luleå tekniska universitet.
    Petersson, Stig
    Luleå tekniska universitet.
    Fragmentering av och metallutvinning ur elektronikskrot1989In: Konferens i mineralteknik: Luleå 14-16 februari 1989 / [ed] Börje Sköld; Eric Forssberg, MinFo , 1989, p. 121-136Conference paper (Other academic)
  • 287.
    Bergman, Dan
    et al.
    Luleå tekniska universitet.
    Petersson, Stig
    Luleå tekniska universitet.
    Metod for fragmentering och metallutvinning av elekronikskrot1987Report (Other academic)
  • 288.
    Bergseth, Ellen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Sosa, Mario
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Andersson, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    A note on the pitting life of IQ steel versus 16MnCr5 steel in a back to back gear test rig2018Conference paper (Refereed)
    Abstract [en]

    IQ-steel is isotropic (i.e. equally strong in all directions), cleaner, and with less inclusions than 16MnCr5 regular gear steel (RS). IQ-steel is used in diesel inlets and for bearings but to date has not been used for gears. Previous studies, has shown good potential to increase the bending fatigue life of gears. The method in this study is a mechanical test procedure to determine the pitting load capacity of gear transmission lubricants, but with the focus on comparing the pitting load capacity of the two steel types IQ-steel with RS. Times to failures, photographs of the fatigue damage are presented in the study. Gear teeth from each steel type were analysed using SEM. The results, which are based on six tests in total (three IQ-steel and three RS-steel gear pairs), indicate that the IQ-steel may have at least similar surface capacity as the regular steel.

    Keywords: Pitting life, Gear, IQ-steel

  • 289. Bergström, Yngve
    et al.
    Granbom, Ylva
    A dislocation model for the stress-strain behavior of dual phase steels2008In: IDDRG 2008 International Conference, 2008Conference paper (Refereed)
    Abstract [en]

    The Bergström dislocation model is used to study the influence of coiling temperature after hot rolling on the mechanical properties of the cold rolled SSAB-grade Docol 800DP. Further, the anisotropy-effect for this type of steel, caused for instance by banding, is investigated. The physical dislocation model is based on the assumption that the work hardening behaviour is controlled by the creation, the immobilisation and the remobilisation of dislocations and it is demonstrated that all these processes are strongly influenced by the amount of hard martensite particles in DP-steels. The true strain to necking is a widely used tool for estimating the stretch formability of DP-steels. A detailed discussion regarding the influence of for instance friction stress, rate of dislocation remobilisation and mean free path of dislocation motion is presented. It is also indicated that the best stretch formability of DP-steel is obtained by minimising the quotient between the rate of work hardening at smaller strains with that at larger strains, close to the strain at necking.

  • 290. Bergström, Yngve
    et al.
    Granbom, Ylva
    Product Development/Materials Research, Borlänge, Sweden.
    Sterkenburg, Dirk
    A dislocation based theory for the deformation hardening behavior of DP-steels: Impact of martensite content and ferrite grain size2010In: Journal of Metallurgy, ISSN 1687-9465, E-ISSN 1687-9473, Vol. 2010, no 647198Article in journal (Refereed)
    Abstract [en]

    A dislocation model, accurately describing the uniaxial plastic stress-strain behavior of dual phase (DP) steels, is proposed and the impact of martensite content and ferrite grain size in four commercially produced DP-steels is analyzed. It is assumed that the plastic deformation process is localized to the ferrite. This is taken into account by introducing a non-homogeneity parameter, f(ε), that specifies the volume fraction of ferrite taking active part in the plastic deformation process. It is found that the larger the martensite content the smaller the initial volume fraction of active ferrite which yields a higher initial deformation hardening rate. This explains the high energy absorbing capacity of DP-steels with high volume fractions of martensite. Further, the effect of ferrite grain size strengthening in DP-steels is important. The flow stress grain size sensitivity for DP-steels is observed to be 7 times larger than that for single phase ferrite.

  • 291.
    Beskow, Kristina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sano, N
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Thermodynamic analysis on the formation and chemical development of non-metallic inclusions in ladle treatment of tool steels2006In: Iron & Steel Technology, ISSN 1547-0423, Vol. 2, p. 103-116Article in journal (Refereed)
  • 292.
    Beskow, Kristina
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Sichen, Du
    KTH, Superseded Departments, Materials Science and Engineering.
    Ladle glaze: major source of oxide inclusions during ladle treatment of steel2004In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 31, no 5, p. 393-400Article in journal (Refereed)
    Abstract [en]

    Samples of ladle lining covered by glaze were taken from industrial ladles of different ages at Uddeholm Tooling AB, Hagfors, Sweden. It was found in the samples taken at and below the slag line that a slag infiltrated layer was covered by an outer layer containing many MgO 'islands' of various sizes. The microstructure of the infiltrating slag was the same as the matrix of the outer layer. The slag was found to decompose into the compound 3CaO. Al2O3 and a liquid phase during the cooling process. The former phase along with tiny MgO particles from the ladle glaze was found to be one of the major sources of inclusions during the degassing and flotation periods of ladle treatment. Thermodynamic analysis indicated that the reaction between the ladle glaze and the slag from the electric arc furnace resulted in the formation of MgO-Al2O3 spinel and an oxide solution, which were also the main inclusions found at the initial stages of ladle treatment. Evidence of this reaction was found in the lining samples taken above the slag line.

  • 293.
    Beskow, Kristina
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Tripathi, Nagendra N.
    KTH, Superseded Departments, Materials Science and Engineering.
    Nzotta, M.
    Sandberg, A.
    Sichen, Du
    KTH, Superseded Departments, Materials Science and Engineering.
    Impact of slag-refractory lining reactions on the formation of inclusions in steel2004In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 31, no 6, p. 514-518Article in journal (Refereed)
    Abstract [en]

    The present study was carried out to investigate the impact of slag-refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.

  • 294.
    Beskow, Kristina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Viswanathan, N. N.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Sichen, Du
    KTH, Superseded Departments, Materials Science and Engineering.
    Study of the deoxidation of steel with aluminum wire injection in a gas-stirred ladle2001In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 32, no 2, p. 319-328Article in journal (Refereed)
    Abstract [en]

    In the present work, the deoxidation of liquid steel with aluminum wire injection in a gas-stirred ladle was studied by mathematical modeling using a computational fluid dynamics (CFD) approach. This was complemented by an industrial trial study conducted at Uddeholm Tooling AB (Hagfors, Sweden). The results of the industrial trials were found to be in accordance with the results of the model calculation. In order to study the aspect of nucleation of alumina, emphasis was given to the initial period of deoxidation, when aluminum wire was injected into the bath. The concentration distributions of aluminum and oxygen were calculated both by considering and not considering the chemical reaction. Both calculations revealed that the driving force for the nucleation of Al2O3 was very high in the region near the upper surface of the bath and close to the wire injection. The estimated nucleation rate in the vicinity of the aluminum wire injection point was much higher than the recommended value for spontaneously homogeneous nucleation, 10(3) nuclei/(cm(3)/s). The results of the model calculation also showed that the alumina nuclei generated at the vicinity of the wire injection point are transported to other regions by the flow.

  • 295. Beyhaghi, Maryam
    et al.
    Kiani-Rashid, Ali-Reza
    Kashefi, Mehrdad
    Khaki, Jalil Vandati
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Effect of powder reactivity on fabrication and properties of NiAl/Al2O3 composite coated on cast iron using spark plasma sintering2015In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 344, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Powder mixtures of Ni, NiO and Al are ball milled for 1 and 10 h. X-ray diffractometry and differential thermal analysis show that while ball milling for 1 h produced mechanically activated powder; 10 h ball milling produced NiAl and Al2O3 phases. Dense NiAl/Al2O3 composite coatings are formed on gray cast iron substrate by spark plasma sintering (SPS) technique. The effect of powder reactivity on microstructure, hardness and scratch hardness of NiAl/Al2O3 coatings after SPS is discussed. Results show that in the coating sample made of mechanically activated powder in situ synthesis of NiAl/Al2O3 composite coating is fulfilled and a thicker well-formed diffusion bond layer at the interface between coating and substrate is observed. The diffusion of elements across the bond layers and phase evolution in the bond layers were investigated. No pores or cracks were observed at the interface between coating layer and substrate in any of samples. Higher Vickers hardness and scratch hardness values in coating made of 10 h ball milled powder than in coating fabricated from 1 h ball milled powder are attributed to better dispersion of Al2O3 reinforcement particles in NiAl matrix and nano-crystalline structure of NiAl matrix. Scratched surface of coatings did not reveal any cracking or spallation at coating-substrate interface indicating their good adherence at test conditions.

  • 296.
    Bhatti, Ayjwat A.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Development of efficient three-dimensional welding simulation approach for residual stress estimation in different welded joints2012In: Journal of Strain Analysis for Engineering Design, ISSN 0309-3247, E-ISSN 2041-3130, Vol. 47, no 8, p. 539-552Article in journal (Refereed)
    Abstract [en]

    Based on the available welding simulation approaches found in the literature, an alternative and simplified welding simulation approach is developed, called rapid dumping. It is a sequential thermomechanical approach, which makes use of the moving heat source in thermal analysis and the block-dumping approach in mechanical analysis for prediction of welding residual stresses in three dimensions. It is first developed for longitudinal stiffener joint and then validated by applying on a butt-welded, T-fillet, and multipass tube-flange joints. The temperature-dependent material properties were obtained using JMat Pro software, a java-based material property simulation software. The material properties were validated with experimentally determined material properties found in the literature. The predicted residual stresses were validated by X-ray diffraction measurements on the longitudinal stiffener fillet-welded joint. Using the rapid-dumping approach, the residual stresses obtained at the weld toe were in qualitatively good agreement with the measured residual stresses. The rapid-dumping approach showed to capture the effects of moving heat source and weld start/stop location. In addition, it has reduced the computational time significantly with a preserved accuracy of the estimated welding residual stresses.

  • 297. Bhatti, Ayjwat Awais
    et al.
    Li, Peigang
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Svensson, Lars Erik
    Samuelsson, Jack
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Classification and crackgrowth modeling of cold lap defects in tandem GMAW welding2011In: International Symposium onFatigue Design & Material Defects, 2011Conference paper (Refereed)
  • 298.
    Bhatti, Tariq M.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Bioleaching of organic carbon rich polymetallic black shale2015In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 157, p. 246-255Article in journal (Refereed)
    Abstract [en]

    The present study describes the extraction of metals from organic-carbon rich Kyrk Tasjo (Sweden) polymetallic black shale using mixed cultures of acidophilic iron- and sulfur-oxidizing microorganisms. Quartz, Mite, micro-cline, calcite, dolomite and pyrite minerals were present in shale matrix. Black shale contained 10.77% organic carbon as kerogen and 1.16% inorganic carbon (graphite). The leaching experiments were performed in shake flasks and stirred tank reactors with and without acidophilic Fe- and S-oxidizing psychrotolerant, mesophile and moderate thermophile strains at 6,30 and 45 degrees C. Biological oxidation of pyrite generated sulfuric acid and ferric sulfate in leach solutions during leaching process. Microbial leaching solubilized 80-90% of the total metals (U, Cu, Ni, Mn, Mo, Y and Zn) after 15-20 days of bioleaching at 30 and 45 degrees C; whereas metal solubilization was slower with acidophilic psychrotolerant bacteria at 6 degrees C. The biodegradation of kerogen released tetradecane (CH3(CH2)(12)CH3), a long-chain aliphatic hydrocarbon compound and several other un-identified hydrocarbons in leach solutions during bioleaching of black shale. The addition of PO43- and NH4+ in the growth medium during bioleaching had no effect or decreased the metal solubilization, suggesting that the microorganisms obtained these nutrients from the minerals and kerogen (C100H112O9N2S5), a nitrogenous hydrocarbon compound present in the shale matrix. Metal dissolution from black shale was mainly attributed to the acid concentration in leach solution and temperature. The leaching data demonstrate the feasibility of extracting metals from the black shale without additional nutrient supply that constitute a cost saving for commercial scale application of bioleaching process. The bioleaching approach does not appear warranted to view of the low concentrations, albeit relatively high recoveries of valuable metals from the black shale. The leaching data indicate that exposed black shale occurrences, being subject to ambient weather conditions, constitute a long term environmental challenge.

  • 299.
    Bhogireddy, Venkata Sai Pavan Kumar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Phase Field modeling of sigma phase transformation in duplex stainless steels: Using FiPy-Finite Volume PDE solver2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Duplex Stainless Steels (DSS) are used extensively in various industrial applications where the properties of both austenite and ferrite steels are required. Higher mechanical strength and superior corrosion resistance are the advantages of DSS. One of the main drawbacks for Duplex steels is precipitation of sigma phase and other intermetallic phases adversely affecting the mechanical strength and the corrosion behavior of the steels. The precipitation of these secondary phases and the associated brittleness can be due to improper heat treatment. The instability in the microstructure of Duplex stainless steels can be studied by understanding the phase transformations especially the ones involving sigma phase. To reduce the time and effort to be put in for experimental work, computational simulations are used to get an initial understanding on the phase transformations.

    The present thesis work is on the phase transformations involving sigma phase for Fe-Cr system and Fe-Cr-Ni system using theoretical approach in 1D and 2D geometries. A phase field model is implemented for the microstructural evolution in DSS in combination with thermodynamic data collected from the Thermo-Calc software. The Wheeler Boettinger McFadden (WBM) model is used for Gibbs energy interpolation of the system.

    FiPy- Finite volume PDE solver written in python is used to simulate the phase transformation conditions first in Fe-Cr system for ferrite-austenite and ferrite-sigma phase transformations. It is then repeated for Fe-Cr-Ni ternary system. In the present study a model was developed for deriving Gibbs energy expression for sigma phase based on the common tangent condition. This model can be used to describe composition constrained phases and stoichiometric phases using the WBM model in phase field modeling. Cogswell’s theory of using phase order variable instead of an interpolating polynomial in the expression for Gibbs energy of whole system is also tried.

  • 300.
    Bi, Yanyan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Three Dimensional Determinations of Inclusions in Ferroalloys and Steel Samples2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloyson the steel cleanness. Thus, the number, morphology, size and composition of inclusions in sixdifferent ferroalloys (FeTi, FeNb, FeSi,SiMn, LC and HC FeCr) were investigatedin this study. This was done in three dimensions (3D) by using a SEM in combination with EDS after electrolytic extraction of the ferroalloy samples. Theresults show that thenon-metallic and metallic inclusions can besuccessfully analyzed on the surface of a film filterafter a separation of the inclusions from the matrix. Overall, the inclusions canbe divided into two categories depending on the melting point. Furthermore, the possible transformation of different kinds of inclusions after their addition to the liquid steel canalso be determined.

    The inclusions and clusters in steel samples of two similar steel grades of high-silicon non-calcium treated (HSiNC) stainless steels were also investigated and compared during ladle treatment and continuous casting. Samples of liquid steel and slag were taken at different stages of the ladle treatment and casting during two plant trials: a low Al steel (LAl) and a high Al steel (HAl). Spherical (SP), irregular and regular (IR) inclusions and clusters (CL) were observed in the samples from both heats. It wasfound that the morphology and composition of inclusions and clusters in both heats were significantly changed during the ladle treatment and casting. Most of inclusions (44-98%) in a low Al steel are MgO-CaO-SiO2-Al2O3spherical inclusions. The compositions of irregular and regularinclusions and clusters in steel samples of a high Al steel were mostly MgO·Al2O3spinel, but also complex sphericalinclusions containing Al2O3-MgO-CaO-SiO2. In addition, the phase stabilitydiagram based on Darken’s quadratic formalism and Redlich-Kister type polynomial was estimated for both heats at a non-infinite solution.

    It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. Therefore, clusters of rare earth metals (REM) were investigated in steel samples of a S30185 stainless steel grade from a pilot trial (PT, 250 kg) and from an industrial heat (IH, 100 t). Samples were taken from the liquid steel at differentholding times after the addition of a mischmetal. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of the holding time. It was found that typical clusters with regular and irregular inclusions were the main type of clusters (69%-98%) in all PT and IH steel samples. The composition of inclusions in clusters corresponded mostly to REM-oxides. The size of clusters that were observed in different samples varied mainly from 2 to 23 μm. In addition, the size and number of most clusters in PT are larger than those in IH samples.

    Largesize inclusions are recognized to be crucially harmful for the mechanical properties of steel products. Therefore, predictionsof the maximum size of Al2O3-CaO spherical inclusions in an Fe-10 mass% Ni alloy have been examined based on two dimensional (2D) and three dimensional (3D) investigations. The effects of the number of measurements and unit volume on the estimated 3D results were also investigated.

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