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  • 1. A. Hosseini, V.
    et al.
    Karlsson, L.
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Swerea KIMAB AB.
    Reccagni, P.
    Wessman, S.
    Engelberg, D.
    Microstructure and functionality of a uniquely graded super duplex stainless steel designed by a novel arc heat treatment method2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 139, p. 390-400Article in journal (Refereed)
    Abstract [en]

    A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures.

  • 2.
    A. Hosseini, Vahid
    et al.
    University West, Sweden ; Innovatum AB, Sweden.
    Karlsson, Leif
    University West, Sweden.
    Örnek, Cem
    RISE - Research Institutes of Sweden, Materials and Production, KIMAB. KTH Royal Institute of Technology, Sweden.
    Reccagni, Pierfrance
    The University of Manchester, UK.
    Wessman, Sten
    University West, Sweden.
    Engelberg, Dirk
    The University of Manchester, UK.
    Microstructure and functionality of a uniquely graded super duplex stainless steel designed by a novel arc heat treatment method2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 139, p. 390-400Article in journal (Refereed)
    Abstract [en]

    A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures. 

  • 3.
    Akhtar, Farid
    et al.
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Askari, Syed Javid
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Shah, Khadijah Ali
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Du, Xueli
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Guo, Shiju
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Microstructure, mechanical properties, electrical conductivity and wear behavior of high volume TiC reinforced Cu-matrix composites2009In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 60, no 4, p. 327-336Article in journal (Refereed)
    Abstract [en]

    This study deals with the processing, microstructure, mechanical properties, electrical conductivity and wear behavior of high volume titanium carbide reinforced copper matrix composites. The microstructural study revealed that the titanium carbide particles were distributed uniformly in the matrix phase. No interface debonding and micro-cracks were observed in the composite. The addition of alloying elements in the copper considerably increased the sintered density and properties. The composite hardness and strength increased with titanium carbide content and alloying elements in the matrix phase. The electrical conductivities of the composites were predicted using three point upper bound and two phase self consistent predictive models. The wear resistance of the composites was studied against high speed steel. Wear mechanisms were discussed by means of microscope observations on the worn surfaces. The ratio of titanium carbide average grain size to the mean free path of the binder was introduced as a parameter to determine wear performance.

  • 4.
    Akhtar, Farid
    et al.
    Institute of Powder Metallurgy, School of Materials Science, University of Science and Technology Beijing, 30 Xue Yuan Road, 100083, Beijing.
    Guo, SJ
    Institute of Powder Metallurgy, School of Materials Science, University of Science and Technology Beijing, 30 Xue Yuan Road, 100083, Beijing.
    Microstructure, mechanical and fretting wear properties of TiC-stainless steel composites2008In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 59, no 1, p. 84-90Article in journal (Refereed)
    Abstract [en]

    This study deals with the processing, microstructure, and wear behavior of TiC-reinforced stainless steel matrix composites, containing 50 to 70 wt.% TiC. Powder technology was used to successfully fabricate the composites. The microstructure of the composite was characterized by scanning electron microscopy. The microstructural study revealed that the TiC particles were distributed uniformly in the steel matrix phase. Interface debonding and microcracks were not observed in the composite. The composite hardness increased with TiC content. The fretting wear resistance of the composites was studied against high speed steel. The wear mechanisms are discussed by means of microscopical observations on the worn surfaces. The wear was severe at higher wear loads and lower TiC content. Microplowing of the stainless steel matrix was found to be the dominant wear mechanism. Heavy microplowing and rapid removal of material from the wear surface was observed at high wear load. The variation of wear loss with volume fraction and mean free path of the binder phase is also reported

  • 5. Azadian, S.
    et al.
    Wei, L-Y.
    Warren, Richard
    Luleå tekniska universitet.
    Delta phase precipitation in inconel 7182004In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 53, no 1, p. 7-16Article in journal (Refereed)
    Abstract [en]

    The precipitation and dissolution kinetics of the δ-phase were studied in three wrought versions and one spray-formed (SF) version of the nickel alloy, Inconel 718. The precipitation in the spray-formed version and one wrought version was followed during isothermal ageing for up to 100 h between 700 and 1000°C. The δ-phase precipitates in the form of nonuniformly distributed thin platelets and an alternative method of measuring volume fraction of this precipitate morphology is proposed. At and above 800°C, the precipitation was measured quantitatively in terms of the volume fraction and platelet thickness distribution. The maximum rate of precipitation occurred at approximately 900°C. The solvus temperature lay between 1005 and 1015°C for Nb contents of 5.06 and 5.41 wt.%, respectively. A study was made of the dissolution of the δ-phase in all four alloys using isochronal treatments and this confirmed the above solvus temperature range. The effect of δ-phase and its dissolution on the grain growth of the alloys was also determined.

  • 6.
    Balachandramurthi, Arun Ramanathan
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Moverare, Johan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Dixit, Nikhil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Deng, Dunyong
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Microstructural influence on fatigue crack propagation during high cycle fatigue testing of additively manufactured Alloy 7182019In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 149, p. 82-94Article in journal (Refereed)
    Abstract [en]

    A study of the microstructure of additively manufactured Alloy 718 was performed in order to better understand the parameters that have an influence on the fatigue properties of the material. The specimens were manufactured using two powder bed fusion techniques – Electron Beam Melting (EBM) and Selective Laser Melting (SLM). Four point bending fatigue tests were performed at room temperature with a stress ratio of R = 0.1 and 20 Hz frequency, on material that was either in hot isostatically pressed (HIP) and solution treated and aged (STA) condition or in STA condition without a prior HIP treatment. The grains in the SLM material in the HIP + STA condition have grown considerably both in the hatch and the contour regions; EBM material, in contrast, shows grain growth only in the contour region. Fractographic analysis of the specimens in HIP + STA condition showed a faceted appearance while the specimens in STA condition showed a more planar crack appearance. The crack propagation occurred in a transgranular mode and it was found that precipitatessuch as NbC, TiN or δ-phase, when present, did not affect the crack path. The areas with larger grains corresponded to the faceted appearance of the fracture surface. This could be attributed to the plastic zone ahead of the crack tip being confined within one grain, in case of the larger grains, which promotes single shear crack growth mode

  • 7. Brunatova, Ereza
    et al.
    Matej, Zdenek
    Oleynikov, Peter
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Vesely, Josef
    Danis, Stanislav
    Popelkova, Daniela
    Kuzel, Radomir
    Thermal stability of titanate nanorods and titania nanowires formed from titanate nanotubes by heating2014In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 98, p. 26-36Article in journal (Refereed)
    Abstract [en]

    The structure of titanate nanowires was studied by a combination of powder X-ray diffraction (XRD) and 3D precession electron diffraction. Titania nanowires and titanate nanorods were prepared by heating of titanate nanotubes. The structure of final product depended on heating conditions. Titanium nanotubes heated in air at a temperature of 850 degrees C decomposed into three phases Na2Ti6O13 (nanorods) and two phases of TiO2 anatase and rutile. At higher temperatures the anatase form of TiO2 transforms into rutile and the nanorods change into rutile nanoparticles. By contrast, in the vacuum only anatase phases of TiO2 were obtained by heating at 900 degrees C. The anatase transformation into ruffle began only after a longer time of heating at 1000 degrees C. For the description of anisotropic XRD line broadening in the total powder pattern fitting by the program MSTRUCT a model of nanorods with elliptical base was included in the software. The model parameters rod length, axis size of the elliptical base, the ellipse flattening parameter and twist of the base could be refined. Variation of particle shapes with temperature was found.

  • 8. Brunatova, Tereza
    et al.
    Popelkova, Daniela
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Oleynikov, Peter
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Danis, Stanislav
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kuzel, Radomir
    Study of titanate nanotubes by X-ray and electron diffraction and electron microscopy2014In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 87, p. 166-171Article in journal (Refereed)
    Abstract [en]

    The structure of titanate nanotubes (Ti-NTs) was studied by a combination of powder X-ray diffraction (PXRD), electron diffraction and high resolution transmission electron microscopy (HRTEM). Ti-NTs are prepared by hydrothermal treatment of TiO2 powder. The structure is identified by powder X-ray diffraction as the one based on the structure of H2Ti2O5 center dot H2O phase. The same structure is obtained by projected potential from HRTEM through-focus image series. The structure is verified by simulated PXRD pattern with the aid of the Debye formula. The validity of the model is tested by computing Fourier transformation of a single nanotube which is proportional to measured electron diffraction intensities. A good agreement of this calculation with measured precession electron diffraction data is achieved.

  • 9.
    Cwirzen, A.
    et al.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Habermehl-Cwirzen, K.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Nasibulin, A. G.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Kaupinen, E. I.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Mudimela, P. R.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Penttala, V.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    SEM/AFM studies of cementitious binder modified by MWCNT and nano-sized Fe needles2009In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 60, no 7, p. 735-740Article in journal (Refereed)
    Abstract [en]

    Several compositions of cement paste samples containing multiwalled carbon nanotubes were produced using a small-size vacuum mixer. The mixes had water-to-binder ratios of 0.25 and 0.3. Sulfate resistant cement has been used. The multiwalled carbon nanotubes were introduced as a water suspension with added surfactant admixtures. The used surfactant acted as plasticizing agents for the cement paste and as dispersant for the multiwalled carbon nanotubes. A set of beams was produced to determine the compressive and flexural strengths. The scanning electron microscope and atomic force microscope studies of fractured and polished samples showed a good dispersion of multiwalled carbon nanotubes in the cement matrix. The studies revealed also sliding of multiwalled carbon nanotubes from the matrix in tension which indicates their weak bond with cement matrix. In addition to multiwalled carbon nanotubes also steel wires covered with ferrite needles were investigated to determine the bond strength between the matrix and the steel wire. These later samples consisted of 15-mm-high cylinders of cement paste with vertically cast-in steel wires. As reference, plain steel wires were cast, too. The bond strength between steel wires covered with nano-sized Fe needles appeared to be lower in comparison with the reference wires. The scanning electron microscope studies of fractured samples indicated on brittle nature of Fe needles resulting in shear-caused breakage of the bond to the matrix. © 2008 Elsevier Inc. All rights reserved.

  • 10. Drar, Hassan
    et al.
    Svensson, Ingvar L
    Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting.
    Characterization of tensile properties and microstructures in directionally solidified Al-Si alloys using linear roughness index2006In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 57, no 4-5, p. 244-258Article in journal (Refereed)
  • 11.
    Esmaily, M.
    et al.
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Shahabi-Navid, M.
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Mortazavi, N.
    Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Svensson, J. E.
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Halvarsson, M.
    Wessen, M.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jarfors, A. E. W.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Johansson, L. G.
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Microstructural characterization of the Mg-Al alloy AM50 produced by a newly developed rheo-casting process2014In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 95, p. 50-64Article in journal (Refereed)
    Abstract [en]

    The microstructure of rheo-cast Mg-Al alloy AM50 produced by the RheoMetal process is investigated and compared with the same alloy produced by conventional high pressure die casting. The size and arrangement of microstructural constituents and pores are characterized quantitatively using image analyzing techniques. The nearest neighbor distribution of the intermetallic particles is determined. The area fraction of porosity in rheo-cast AM50 is about half that found in the high pressure die cast alloy. In rheo-cast material, the distribution of p phase (Mg17Al12) is relatively uniform throughout the cast. In contrast, the beta phase particles tend to form macroscopic agglomerates in high pressure die cast material. The externally solidified grains in the rheo-cast material exhibit a smaller aluminum gradient than in the high pressure die cast alloy. This indicates that the solidification of the rheo-cast material is closer to equilibrium. (C) 2014 Elsevier Inc. All rights reserved.

  • 12.
    Fargas, G.
    et al.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Roa, J. J.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Sefer, B.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain. University of Erlangen-Nuremberg, Institute for Surface Science and Corrosion, Department of Materials Science and Engineering, Erlangen, D-91058, Germany.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Antti, M. -L
    Division of Materials Science, Luleå University of Technology, Luleå, S-97187, Sweden.
    Mateo, A.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Influence of cyclic thermal treatments on the oxidation behavior of Ti-6Al-2Sn-4Zr-2Mo alloy2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 145, p. 218-224Article in journal (Refereed)
    Abstract [en]

    Ti-6Al-2Sn-4Zr-2Mo is one of the most common titanium alloys for aerospace industry. This alloy experiences oxidation phenomenon at elevated temperatures. In the present study, cyclic thermal treatments were performed in air at 500, 593 and 700 °C, up to 500 cycles, in order to determine the oxidation kinetics and to analyze the oxide scale and alpha-case formation. Moreover, results were compared to those achieved under isothermal conditions to elucidate differences between both thermal conditions. In this sense, metallographic techniques and X-ray diffraction, together with a detailed advanced characterization of the microstructure by Field Emission Scanning Electron Microscopy and Focus Ions Beam, were used to analyze surface oxidation evolution. Results pointed out that cyclic treatments induced a strong increase of the weight gain compared to isothermal treatments. The analysis of the oxide scale revealed the formation of not only rutile, as isothermal treatments, but also anatase. Thickness of the oxide scale was higher for cyclic conditions, while alpha case did not exceed values reached by isothermal treatments and even became lower at 500 °C.

  • 13.
    Fargas, G.
    et al.
    CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona 08019, Spain , .
    Roa, J.J.
    CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona 08019, Spain.
    Sefer, Birhan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona 08019, Spain.
    Pedersen, R.
    Division of Subtractive and Additive Manufacturing, University West, S-46186 Trollhaettan.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Matteo, A.
    CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona 08019, Spain.
    Influence of cyclic thermal treatments on the oxidation behavior of Ti-6Al-2Sn-4Zr-2Mo alloy2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 145, p. 218-224Article in journal (Refereed)
    Abstract [en]

    Ti-6Al-2Sn-4Zr-2Mo is one of the most common titanium alloys for aerospace industry. This alloy experiences oxidation phenomenon at elevated temperatures. In the present study, cyclic thermal treatments were performed in air at 500, 593 and 700 °C, up to 500 cycles, in order to determine the oxidation kinetics and to analyze the oxide scale and alpha-case formation. Moreover, results were compared to those achieved under isothermal conditions to elucidate differences between both thermal conditions. In this sense, metallographic techniques and X-ray diffraction, together with a detailed advanced characterization of the microstructure by Field Emission Scanning Electron Microscopy and Focus Ions Beam, were used to analyze surface oxidation evolution. Results pointed out that cyclic treatments induced a strong increase of the weight gain compared to isothermal treatments. The analysis of the oxide scale revealed the formation of not only rutile, as isothermal treatments, but also anatase. Thickness of the oxide scale was higher for cyclic conditions, while alpha case did not exceed values reached by isothermal treatments and even became lower at 500 °C.

  • 14. Gaddam, Raghuveer
    et al.
    Sefer, Birhan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pederson, Robert
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oxidation and alpha–case formation in Ti–6Al–2Sn–4Zr–2Mo alloy2015In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 99, p. 166-174Article in journal (Refereed)
    Abstract [en]

    Isothermal heat treatments in ambient air were performed on wrought Ti–6Al–2Sn–4Zr–2Mo (Ti–6242) material at 500, 593 and 700 °C for times up to 500 hours. In presence of oxygen at elevated temperatures simultaneous reactions occurred in Ti–6242 alloy, which resulted in formation of an oxide scale and a layer with higher oxygen concentration (termed as alpha–case). Total weight gain analysis showed that there was a transition in the oxidation kinetics. At 500 °C, the oxidation kinetics obeyed cubic relationship up to 200 hours and thereafter changed to parabolic at prolonged exposure times. At 593 °C, it followed parabolic relationship. After heat treatment at 700 °C, the oxidation obeyed parabolic relationship up to 200 hours and thereafter changed to linear at prolonged exposure times. The observed transition is believed to be due to the differences observed in the oxide scale. The activation energy for parabolic oxidation was estimated to be 157 kJ/mol. In addition, alpha–case layer was evaluated using optical microscope, electron probe micro analyser and microhardness tester. The thickness of the alpha–case layer was found to be a function of temperature and time, increasing proportionally, and following parabolic relationship. The activation energy for formation of alpha–case layer was estimated to be 153 kJ/mol.

  • 15.
    Hernando, Juan Carlos
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Ghassemali, Ehsan
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Diószegi, Attila
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    The morphological evolution of primary austenite during isothermal coarsening2017In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 131, p. 492-499Article in journal (Refereed)
    Abstract [en]

    The morphological evolution of primary austenite in an industrial hypoeutectic lamellar cast iron was studied under isothermal conditions for coarsening times varying from 0 min to 96 h. The dendritic austenite structure formed during the primary solidification suffered major morphological changes during the isothermal coarsening process. After a sufficient coarsening time, dendrite fragmentation, globularization, and coalescence of austenite were studied using electron backscatter diffraction (EBSD) technique. This study confirmed that the secondary dendrite arm spacing (SDAS) is an inappropriate length scale to describe the primary austenite coarsening process for longer times. The application of shape independent quantitative parameters confirmed the reduction of the total interfacial area during microstructural coarsening. The modulus of the primary austenite, Mγ, which represents the volume-surface ratio for the austenite phase, and the spatial distribution of the austenite particles, measured as the nearest distance between the center of gravity of neighboring particles, Dγ, followed a linear relation with the cube root of coarsening time during the whole coarsening process. The mean curvature of the austenite interface, characterized through stereological relations, showed a linear relation to Mγ and Dγ, allowing the quantitative characterization and modeling of the complete coarsening process of primary austenite.

    The full text will be freely available from 2019-07-18 00:00
  • 16.
    Hosseini, Vahid
    et al.
    University West, Department of Engineering Science, Division of Welding Technology. Innovatum AB., Trollhättan, Trollhättan, Sweden.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Örnek, Cem
    KTH Royal Institute of Technology, Department of Chemical Science and Engineering, Division of Surface and Corrosion Science, Stockholm, Sweden, Department of Corrosion in Energy and Processing Industry, Swerea KIMAB AB, P.O. Box 7047, Kista, Sweden.
    Reccagni, Pierfranco
    The University of Manchester, School of Materials, Manchester, United Kingdom.
    Wessman, Sten
    University West, Department of Engineering Science, Division of Welding Technology.
    Engelberg, Dirk
    The University of Manchester, School of Materials, Manchester, United Kingdom.
    Microstructure and functionality of a uniquely graded super duplex stainless steel designed by a novel arc heat treatment method2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 139, p. 390-400Article in journal (Refereed)
    Abstract [en]

    A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures. © 2018 The Authors

  • 17.
    Karimi Neghlani, Paria
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sadeghi, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ålgårdh, Joakim
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Powder Materials & Additive Manufacturing, Swerea KIMAB AB, Kista, 164 40, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics2019In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 148, p. 88-99Article in journal (Refereed)
    Abstract [en]

    Electron beam melting-powder bed fusion (EBM-PBF) is an additive manufacturing process, which is able to produce parts in layer-by-layer fashion from a 3D model data. Currently application of this technology in parts manufacturing with high geometrical complexity has acquired growing interest in industry. To recommend the EBM process into industry for manufacturing parts, improved mechanical properties of final part must be obtained. Such properties highly depend on individual single melted track and single layer. In EBM, interactions between the electron beam, powder, and solid underlying layer affect the geometrical (e.g., re-melt depth, track width, contact angle, and track height) and microstructural (e.g., grain structure, and primary dendrite arm spacing) characteristics of the melted tracks. The core of the present research was to explore the influence of linear energy input parameters in terms of beam scanning speed, beam current as well as focus offset and their interactions on the geometry and microstructure of EBM-manufactured single tracks of Alloy 718. Increased scanning speed led to lower linear energy input values (<0.9 J/mm) in an specific range of the focus offset (0–10 mA) which resulted in instability, and discontinuity of the single tracks as well as balling effect. Decreasing the scanning speed and increasing the beam current resulted in higher melt pool depth and width. By statistical evaluations, the most influencing parameters on the geometrical features were primarily the scanning speed, and secondly the beam current. Primary dendrite arm spacing (PDAS) slightly decreased by increasing the scanning speed using lower beam current values as the linear energy input decreased. By increasing the linear energy input, the chance of more equiaxed grain formation was high, however, at lower linear energy input, mainly columnar grains were observed. The lower focus offset values resulted in more uniform grains along the 〈001〉 crystallographic direction. © 2018 Elsevier Inc. 

  • 18.
    Karimi, Paria
    et al.
    University West, Sweden.
    Sadeghi, Esmaeil
    University West, Sweden.
    Ålgårdh, Joakim
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB. University West, Sweden.
    Andersson, Joel
    University West, Sweden.
    EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics2019In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 148, p. 88-99Article in journal (Refereed)
    Abstract [en]

    Electron beam melting-powder bed fusion (EBM-PBF) is an additive manufacturing process, which is able to produce parts in layer-by-layer fashion from a 3D model data. Currently application of this technology in parts manufacturing with high geometrical complexity has acquired growing interest in industry. To recommend the EBM process into industry for manufacturing parts, improved mechanical properties of final part must be obtained. Such properties highly depend on individual single melted track and single layer. In EBM, interactions between the electron beam, powder, and solid underlying layer affect the geometrical (e.g., re-melt depth, track width, contact angle, and track height) and microstructural (e.g., grain structure, and primary dendrite arm spacing) characteristics of the melted tracks. The core of the present research was to explore the influence of linear energy input parameters in terms of beam scanning speed, beam current as well as focus offset and their interactions on the geometry and microstructure of EBM-manufactured single tracks of Alloy 718. Increased scanning speed led to lower linear energy input values (<0.9 J/mm) in an specific range of the focus offset (0–10 mA) which resulted in instability, and discontinuity of the single tracks as well as balling effect. Decreasing the scanning speed and increasing the beam current resulted in higher melt pool depth and width. By statistical evaluations, the most influencing parameters on the geometrical features were primarily the scanning speed, and secondly the beam current. Primary dendrite arm spacing (PDAS) slightly decreased by increasing the scanning speed using lower beam current values as the linear energy input decreased. By increasing the linear energy input, the chance of more equiaxed grain formation was high, however, at lower linear energy input, mainly columnar grains were observed. The lower focus offset values resulted in more uniform grains along the 〈001〉 crystallographic direction.

  • 19.
    Kasvayee, Keivan Amiri
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Ghassemali, Ehsan
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Salomonsson, Kent
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Sujakhu, Surendra
    Nanyang Technological University, School of Mechanical and Aerospace Engineering, Singapore.
    Castagne, Sylvie
    KU Leuven, Department of Mechanical Engineering, Leuven, Belgium.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Microstructural strain mapping during in-situ cyclic testing of ductile iron2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 140, p. 333-339Article in journal (Refereed)
    Abstract [en]

    This paper focuses on local strain distribution in the microstructure of high silicon ductile iron during cyclic loading. In-situ cyclic test was performed on compact-tension (CT) samples inside the scanning electron microscope (SEM) to record the whole deformation and obtain micrographs for microstructural strain measurement by means of digital image correlation (DIC) technique. Focused ion beam (FIB) milling was used to generate speckle patterns necessary for DIC measurement. The equivalent Von Mises strain distribution was measured in the microstructure at the maximum applied load. The results revealed a heterogeneous strain distribution at the microstructural level with higher strain gradients close to the notch of the CT sample and accumulated strain bands between graphite particles. Local strain ahead of the early initiated micro-cracks was quantitatively measured, showing high strain localization, which decreased by moving away from the micro-crack tip. It could be observed that the peak of strain in the field of view was not necessarily located ahead of the micro-cracks tip which could be because of the (i) strain relaxation due to the presence of other micro-cracks and/or (ii) presence of subsurface microstructural features such as graphite particles that influenced the strain concentration on the surface.

    The full text will be freely available from 2020-04-12 00:00
  • 20.
    Kazantseva, N.
    et al.
    Institute of Metal Physics, Russia; Ural Federal University, Russia.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Thuvander, M.
    Chalmers University of Technology, Sweden.
    Yadroitsev, I.
    Central University of Technology, South Africa.
    Vinogradova, N.
    Institute of Metal Physics, Russia.
    Ezhov, I.
    Institute of Metal Physics, Russia.
    Martensitic transformations in Ti-6Al-4V (ELI) alloy manufactured by 3D Printing2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 146, p. 101-112Article in journal (Refereed)
    Abstract [en]

    In the present investigation, Ti-6Al-4V ELI samples were manufactured by the powder-bed fusion (PBF) process using the laser sintering (LS) technology. Microstructure, chemical and phase constitution, and mechanical properties were studied by means of the transmission electron microscopy, atom probe tomography, X-ray diffraction, nanoindentation and mechanical testing. It was found that the structure of LS samples consisted of two different variants of metastable phases, namely the hexagonal alpha' martensitic phase and small amounts of the orthorhombic alpha '' martensitic phase. The martensitic alpha'-phase was formed because of the high cooling rates of the LS method, The {10 (1) over bar2} <(1) over bar 011 > hexagonal martensite tensile twins were observed in the microstructure of the as-build alloy. Small areas with inner twinning martensitic plates, which are typical for the metastable orthor-hombic martensitic phase in titanium alloys, were identified by the transmission electron microscopy. Atom probe tomography (APT) confirmed localization of beta-stabilizing elements at interfaces, presumably at the twin or lamella boundaries. The structure and origin of the martensitic phases in 3D printed Ti-6Al-4V alloys are discussed with respect to in-situ heat treatment during manufacturing.

  • 21. Koppoju, S.
    et al.
    Shariff, S. M.
    Singh, A. K.
    Mantripragada, R.
    Gadhe, P.
    Joshi, S. V.
    Evolution of texture during laser surface treatment of an austenitic manganese steel2015In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 102, p. 29-34Article in journal (Refereed)
    Abstract [en]

    This work describes the evolution of microstructure and texture of an austenitic manganese steel (1.34C-13.6Mn-0.45Si-Fe, wt.%) during surface modification using a high power diode laser. Strong (002) texture has been observed on the surface of the steel with increase in interaction time. It has been found that columnar type dendrites are responsible for the strong texture which is favorably grown in the < 001 > direction perpendicular to the substrate plane. The growth of dendrites with specific crystallographic direction is governed by the interfacial energy anisotropy and thermal gradient direction. (C) 2015 Elsevier Inc. All rights reserved.

  • 22. Lombardi, A.
    et al.
    Mu, Wangzhong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ravindran, C.
    Dogan, N.
    Barati, M.
    In-situ investigation of incipient melting in a 319 type Al alloy using laser scanning confocal microscopy2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 141, p. 328-337Article in journal (Refereed)
    Abstract [en]

    The modified 319 Al alloy system has been used extensively in precision sand casting of automotive powertrain applications such as engine blocks and cylinder heads, with significant improvement in vehicle fuel efficiency. However, a concern in elevated temperature processing of Al alloys, such as heat treatment and hot working processes, is incipient melting of secondary phases, which is deleterious to mechanical properties. In this study, the laser scanning confocal microscopy (LSCM) technique was used in the analysis of in-situ changes in microstructure as a result of incipient melting. Microstructural analysis was carried out prior to and following elevated temperature exposure in the LSCM using optical microscopy, SEM and EDX. The results suggest that incipient melting of the Al-Al2Cu-Al5Mg8Cu2Si6 ternary eutectic clusters was initiated by the formation of a liquid film which propagated rapidly from the eutectic clusters, coating the Al dendrites in regions adjacent to the eutectic clusters. Following film formation, the ternary eutectic clusters melted completely. Incipient melting also resulted in a localized change in composition in the interdendritic channels as supported by a change in cluster morphology from eutectic to a combination of coarse blocky Al-Cu-Ni and Si particles, and ultra-fine eutectic.

  • 23.
    Lundberg, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Saarimäki, Jonas
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Calmunger, Mattias
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Surface Integrity and Fatigue Behaviour of Electric Discharged Machined and Milled Austenitic Stainless Steel2017In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 124, p. 215-222Article in journal (Refereed)
    Abstract [en]

    Machining of austenitic stainless steels can result in different surface integrities and different machining process parameters will have a great impact on the component fatigue life. Understanding how machining processes affect the cyclic behaviour and microstructure are of outmost importance in order to improve existing and new life estimation models. Milling and electrical discharge machining (EDM) have been used to manufacture rectangular four-point bend fatigue test samples; subjected to high cycle fatigue. Before fatigue testing, surface integrity characterisation of the two surface conditions was conducted using scanning electron microscopy, surface roughness, residual stress profiles, and hardness profiles. Differences in cyclic behaviour were observed between the two surface conditions by the fatigue testing. The milled samples exhibited a fatigue limit. EDM samples did not show the same behaviour due to ratcheting. Recrystallized nano sized grains were identified at the severely plastically deformed surface of the milled samples. Large amounts of bent mechanical twins were observed ~ 5 μm below the surface. Grain shearing and subsequent grain rotation from milling bent the mechanical twins. EDM samples showed much less plastic deformation at the surface. Surface tensile residual stresses of ~ 500 MPa and ~ 200 MPa for the milled and EDM samples respectively were measured.

  • 24. Morcillo, M.
    et al.
    Chang, Tingru
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Chico, B.
    de la Fuente, D.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Jimenez, J. A.
    Leygraf, Christopher
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Characterisation of a centuries-old patinated copper roof tile from Queen Anne's Summer Palace in Prague2017In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 133, p. 146-155Article in journal (Refereed)
    Abstract [en]

    This paper presents an in-depth characterisation study of the patina formed on a copper tile taken from the roof of Queen Anne's Summer Palace in Prague after > 300 years of exposure to the action of the atmosphere. A wide variety of techniques have been used, including metallographic and chemical analysis (electrogravimetry, AAS, XRF) of the copper matrix, and spectroscopic and microscopic investigations (GIXRD, FTIR, TEM/EDS and SEM/ EDS) to determine the composition and structure of the patina. The major conclusions of the study are: (a) the base copper contains abundant inclusions mainly of rosiaite (PbSb2O6); (b) the patina is formed by an inner sublayer of cuprite (Cu2O) and an outer sublayer of brochantite [Cu4SO4(OH)(6)] and antlerite [Cu3SO4(OH)(4)] and traces of azurite [Cu-3(CO3)(2)(OH)(2)]; and (c) the brochantite/antlerite crystals are randomly doped with Fe and C.

  • 25.
    Neikter, Magnus
    et al.
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Åkerfeldt, P.
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Antti, M. -L
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Microstructural characterization and comparison of Ti-6Al-4V manufactured with different additive manufacturing processes2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 143, p. 68-75Article in journal (Refereed)
    Abstract [en]

    In this work, the microstructures of Ti-6Al-4V manufactured by different additive manufacturing (AM) processes have been characterized and compared. The microstructural features that were characterized are the α lath thickness, grain boundary α (GB-α) thickness, prior β grain size and α colony size. In addition, the microhardnesses were also measured and compared. The microstructure of shaped metal deposited (SMD) Ti-6Al-4V material showed the smallest variations in α lath size, whereas the material manufactured with laser metal wire deposition-0 (LMwD-0) showed the largest variation. The prior β grain size was found to be smaller in material manufactured with powder bed fusion (PBF) as compared with corresponding material manufactured with the directed energy deposition (DED) processes. Parallel bands were only observed in materials manufactured with DED processes while being non-present in material manufactured with PBF processes.

  • 26.
    Neikter, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Åkerfeldt, Pia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pederson, Robert
    Division of Welding Technology, University West, Trollhättan 461 32, Sweden.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Microstructural characterization and comparison of Ti-6Al-4V manufactured with different additive manufacturing processes2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 143, no SI, p. 68-75Article in journal (Refereed)
    Abstract [en]

    In this work, the microstructures of Ti-6Al-4V manufactured by different additive manufacturing (AM) processes have been characterized and compared. The microstructural features that were characterized are the α lath thickness, grain boundary α (GB-α) thickness, prior β grain size and α colony size. In addition, the microhardnesses were also measured and compared. The microstructure of shaped metal deposited (SMD) Ti-6Al-4V material showed the smallest variations in α lath size, whereas the material manufactured with laser metal wire deposition-0 (LMwD-0) showed the largest variation. The prior β grain size was found to be smaller in material manufactured with powder bed fusion (PBF) as compared with corresponding material manufactured with the directed energy deposition (DED) processes. Parallel bands were only observed in materials manufactured with DED processes while being non-present in material manufactured with PBF processes.

  • 27.
    Olsén, Jon
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Leifeng
    Koptyug, Andrey
    Rannar, Lars-Erik
    Micro- and macro-structural heterogeneities in 316L stainless steel prepared by electron-beam melting2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 141, p. 1-7Article in journal (Refereed)
    Abstract [en]

    This is a study of the micro- and macrostructural variations in samples of stainless steel with the overall composition of the grade 316L, produced using electron beam melting. Electron beam melting is one of the processing methods under consideration for manufacturing some of the International Thermo- Nuclear Experimental Reactor In-Vessel components. Therefore further studies of the homogeneity of the material were conducted. Electron beam melting results in a complicated thermal history of the manufactured part giving a significant impact on the microstructure. A cellular structure that is often observed in samples prepared by selective laser melting was found in the top layers of the specimens. Further down, the structure changed until the cellular structure was almost non-existing, and the grain boundaries had become more pronounced. This revelation of a heterogeneous structure throughout the entire part is crucial for large-scale industrial applications like the Thermo- Nuclear Experimental Reactor to make sure that it is understood that the properties of the material might not be the same at every point, as well as to assure that the correct post-treatment is done. It is also exposed that a significant part of this change is due to molybdenum redistribution inside the sample when it diffuses from the cell boundaries into the cells, and into bigger agglomerates in the grain boundaries. This diffusion seems not to affect the microhardness of the samples.

  • 28.
    Olsén, Jon
    et al.
    Stockholm University.
    Shen, Zhijian
    Stockholm University.
    Liu, Leifeng
    University of Birmingham, Birmingham, United Kingdom.
    Koptyug, Andrey
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Rännar, Lars-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Micro- and macro-structural heterogeneities in 316L stainless steel prepared by electron-beam melting2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 141, p. 1-7Article in journal (Refereed)
    Abstract [en]

    This is a study of the micro- and macrostructural variations in samples of stainless steel with the overall composition of the grade 316L, produced using electron beam melting. Electron beam melting is one of the processing methods under consideration for manufacturing some of the International Thermo- Nuclear Experimental Reactor In-Vessel components. Therefore further studies of the homogeneity of the material were conducted. Electron beam melting results in a complicated thermal history of the manufactured part giving a significant impact on the microstructure. A cellular structure that is often observed in samples prepared by selective laser melting was found in the top layers of the specimens. Further down, the structure changed until the cellular structure was almost non-existing, and the grain boundaries had become more pronounced. This revelation of a heterogeneous structure throughout the entire part is crucial for large-scale industrial applications like the Thermo- Nuclear Experimental Reactor to make sure that it is understood that the properties of the material might not be the same at every point, as well as to assure that the correct post-treatment is done. It is also exposed that a significant part of this change is due to molybdenum redistribution inside the sample when it diffuses from the cell boundaries into the cells, and into bigger agglomerates in the grain boundaries. This diffusion seems not to affect the microhardness of the samples. 

  • 29.
    Sadeghi, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Karimi Neghlani, Paria
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Momeni, Soroush
    Friedrich-Alexander University Erlangen-Nurnberg, Department of Materials Science and Engineering, Erlangen, 91058, Germany.
    Seifi, Mohsen
    Case Western Reserves University, Department of Materials Science & Engineering, Cleveland, 44106,USA; ASTM International, Washington, DC 20036, United States .
    Eklund, Anders
    Quintus Technologies AB, Västerås, 721 66, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 7182019In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 150, p. 236-251Article in journal (Refereed)
    Abstract [en]

    The effect of thermal post treatments consisting of heat treatment (HT), hot isostatic pressing (HIP), and combined HIP-HT on microstructure and oxidation behavior of Alloy 718 manufactured by electron beam powder bed fusion (EB-PBF) technique was investigated. Oxidation of the as-built and post-treated specimens was performed in ambient air at 650, 750, and 850 °C for up to 168 h. Directional columnar-grained microstructure, pores and fine Nb-rich carbides were observed in the as-built specimen. The HT specimen presented the columnar microstructure, plate-like δ phase at grain boundaries, and pores. The dominant grain crystallographic orientation was changed from 〈001〉 in the as-built specimen to 〈101〉 after HT. No grain boundary δ phase was observed in the HIPed specimen, but recrystallization occurred in both the HIP and HIP-HT specimens due to a rapid cooling after HIPing motivating the nucleation of fine grains with limited time to grow. After oxidation exposure at 650 and 750 °C for 168 h, no big difference between weight changes of the as-built and post-treated specimens was noted, whereas at 850 °C, the combined HIP-HT specimen showed the most promising corrosion resistance with the least weight change. At 850 °C, a protective scale of Cr 2 O 3 rich in Cr, Ti, and Ni as well as an internal oxide (branched structure of alumina) developed in all the specimens, while, only a protective Cr 2 O 3 scale was found at 650 and 750 °C. The HIP-HT specimen at 850 °C developed an oxide scale, which was denser and more adherent in comparison to the oxide scales formed on the other three specimens, associated with its limited defect distribution and more homogenized microstructure. Moreover, the δ phase formed close to the surface of the exposed specimens during the oxidation exposure at 850 °C most probably led to nucleation and growth of the oxide scale. © 2019 Elsevier Inc.

  • 30. Saeidi, Kamran
    et al.
    Olsen, Jon
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Scaled down microstructure hierarchy and local heterogeneity in laser melted 316L stainless steelIn: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189Article in journal (Refereed)
  • 31.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Ojo, Olanrewaju
    University of Manitoba,Department of Mechanical Engineering, Winnipeg, R3T 5V6, Canada.
    Microstructural Characterization of Laser Metal Powder Deposited Alloy 7182018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 142, p. 550-559Article in journal (Refereed)
    Abstract [en]

    A microstructural study of Laser Metal Powder Deposition (LMPD) of Alloy 718, using a low (40 J/mm) and high (100 J/mm) heat inputs (HIs) was performed. The microstructure was characterized in as-deposited condition as well as after a standard heat-treatment, using optical microscope (OM), scanning electron microscope (SEM) and Transmission Electron Microscope (TEM). Laves, MC-carbides, γ' and γ'' are observed in the interdendritic areas of both conditions. However, the dendritic core only consists of γ-matrix. The high HI condition shows a slightly larger Primary Dendrite Arm Spacing (PDAS) as compared to the low HI condition. Additionally, the particle size of the Nb-rich constituents in the interdendriticregions (Laves-phase and Niobium carbide) are larger in the high HI sample. After heat-treatment, the Laves phase dissolves and is replaced by δ-phase in the interdendritic regions, while γ', γ'' and MC-carbideremain in the interdendritic regions. However, the γ'' precipitates seems to be less developed in the dendritic core as compared to the interdendritic regions, especially in the high HI sample. This can be attributed to a heterogeneous distribution of Nb in the microstructure, with a lower Nb content in the dendritic core as compared to close to the interdendritic regions.

  • 32. Vazehrad, S.
    et al.
    Elfsberg, J.
    Diószegi, Attila
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals. Jönköping University, Sweden.
    Study of microstructure and silicon segregation in cast iron using color etching and electron microprobe analysis2015In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 104, p. 132-138Article in journal (Refereed)
    Abstract [en]

    An investigation on silicon segregation of lamellar, compacted and nodular graphite iron was carried out by applying a selective, immersion color etching and a modified electron microprobe to study the microstructure. The color etched micrographs of the investigated cast irons by revealing the austenite phase have provided data about the chronology and mechanism of microstructure formation. Moreover, electron microprobe has provided two dimensional segregation maps of silicon. A good agreement was found between the segregation profile of silicon in the color etched microstructure and the silicon maps achieved by electron microprobe analysis. However, quantitative silicon investigation was found to be more accurate than color etching results to study the size of the eutectic colonies.

  • 33. Westraadt, J. E.
    et al.
    Olivier, E. J.
    Neethling, J. H.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Xu, X.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Steuwer, A.
    A high-resolution analytical scanning transmission electron microscopy study of the early stages of spinodal decomposition in binary Fe-Cr2015In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 109, p. 216-221Article in journal (Refereed)
    Abstract [en]

    Spinodal decomposition (SD) is an important phenomenon in materials science and engineering. For example, it is considered to be responsible for the 475 degrees C embrittlement of stainless steels comprising the bcc (ferrite) or bct (martensite) phases. Structural characterization of the evolving minute nano-scale concentration fluctuations during SD in the Fe-Cr system is, however, a notable challenge, and has mainly been considered accessible via atom probe tomography (APT) and small-angle neutron scattering. The standard tool for nanostructure characterization, viz, transmission electron microscopy (TEM), has only been successfully applied to late stages of SD when embrit-dement is already severe. However, we here demonstrate that the structural evolution in the early stages of SD in binary Fe-Cr, and alloys based on the binary, are accessible via analytical scanning TEM. An Fe-36 wt% Cr alloy aged at 500 degrees C for 1, 10 and 100 h is investigated using an aberration-corrected microscope and it is found that highly coherent and interconnected Cr-rich regions develop. The wavelength of decomposition is rather insensitive to the sample thickness and it is quantified to 2, 3 and 6 nm after ageing for 1, 10 and 100 h, which is in reasonable agreement with prior APT analysis. The concentration amplitude is more sensitive to the sample thickness and acquisition parameters but the TEM analysis is in good agreement with APT analysis for the longest ageing time. These findings open up for combinatorial TEM studies where both local crystallography and chemistry is required.

  • 34. Wu, R.
    et al.
    Pettersson, N.
    Martinsson, Å.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Cell structure in cold worked and creep deformed phosphorus alloyed copper2014In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 90, p. 21-30Article in journal (Refereed)
    Abstract [en]

    Transmission electron microscopy (TEM) examinations on as-received, cold worked, as well as cold worked and creep tested phosphorus-alloyed oxygen-free copper (Cu-OFP) have been carried out to study the role of the cell structure. The cell size decreased linearly with increasing plastic deformation in tension. The flow stress in the tests could also be correlated to the cell size. The observed relation between the flow stress and the cell size was in excellent agreement with previously published results. The dense dislocation walls that appeared after cold work in tension is likely to be the main reason for the dramatic increase in creep strength. The dense dislocation walls act as barriers against dislocation motion and their presence also reduces the recovery rate due to an unbalanced dislocation content.

  • 35.
    Wu, Rui
    et al.
    RISE, Swerea, Swerea KIMAB.
    Pettersson, Niklas
    RISE, Swerea, Swerea KIMAB.
    Martinsson, Åsa
    RISE, Swerea, Swerea KIMAB.
    Sandström, Rolf
    RISE, Swerea, Swerea KIMAB.
    Cell structure in cold worked and creep deformed phosphorus alloyed copper2014In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 90, p. 21-30Article in journal (Refereed)
    Abstract [en]

    Transmission electron microscopy (TEM) examinations on as-received, cold worked, as well as cold worked and creep tested phosphorus-alloyed oxygen-free copper (Cu-OFP) have been carried out to study the role of the cell structure. The cell size decreased linearly with increasing plastic deformation in tension. The flow stress in the tests could also be correlated to the cell size. The observed relation between the flow stress and the cell size was in excellent agreement with previously published results. The dense dislocation walls that appeared after cold work in tension is likely to be the main reason for the dramatic increase in creep strength. The dense dislocation walls act as barriers against dislocation motion and their presence also reduces the recovery rate due to an unbalanced dislocation content. © 2014 Elsevier Inc.

  • 36.
    Yang, Jie
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. University of Politecn Cataluna, Spain.
    Roa, J. J.
    University of Politecn Cataluna, Spain; University of Politecn Cataluna, Spain.
    Schwin, M.
    SECO Tools AB, Sweden.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Johansson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. SECO Tools AB, Sweden.
    Llanes, L.
    University of Politecn Cataluna, Spain; University of Politecn Cataluna, Spain.
    Grinding-induced metallurgical alterations in the binder phase of WC-Co cemented carbides2017In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 134, p. 302-310Article in journal (Refereed)
    Abstract [en]

    The metallic binder phase dictates the toughening behavior of WC-Co cemented carbides (hardmetals), even though it occupies a relative small fraction of the composite. Studies on deformation and phase transformation of the binder constituent are scarce. Grinding represents a key manufacturing step in machining of hardmetal tools, and is well-recognized to induce surface integrity alterations. In this work, metallurgical alterations of the binder phase in ground WC-Co cemented carbides have been assessed by a combination of electron back scattered diffraction and transmission electron microscopy techniques. The Co-base binder experiences a martensitic phase transformation from fcc to hcp crystal structure, predominantly in the first 5 mu m below the surface. The hcp fraction decreases gradually along a depth of 10 mu m. Surface Co displays severe plastic deformation under the highest strain, resulting in formation of nanocrystalline grains in the first micrometer below the surface. Microstructural refinement within the binder phase is observed even at greater depth. Stacking faults were detected in most of the refined grains. The metallurgical alterations of the binder phase modify the local stress distribution during grinding, which affects the discerned subsurface microcracking. The resulting residual stress profile is the sum of multiple subsurface changes, such as phase transformation, severe plastic deformation and grain refinement, where it is discerned that the depth profile of the transformed hcp-Co fraction coincides with the grinding-induced residual stress profile.

  • 37.
    Yvell, Karin
    et al.
    Material Science, Dalarna University, Falun, Sweden.
    Grehk, Mikael
    Engberg, Göran
    Microstructure characterization of 316L deformed at high strain rates using EBSD2016In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 122, p. 14-21Article in journal (Refereed)
    Abstract [en]

    Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s− 1 at room temperature and 500 �C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2� can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneous and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain.

  • 38.
    Yvell, Karin
    et al.
    Materials Science, Dalarna University, Falun, Sweden.
    Grehk, Mikael
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Borgenstam, Annika
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Engberg, Göran
    EBSD analysis of surface and bulk microstructure evolution during interrupted tensile testing of a Fe-19Cr-12Ni alloy2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 141, p. 8-18Article in journal (Refereed)
    Abstract [en]

    The microstructure evolution in both surface and bulk grains in a pure Fe-19Cr-12Ni alloy has been analyzed using electron backscatter diffraction after tensile testing interrupted at different strains. Surface grains were studied during in situ tensile testing performed in a scanning electron microscope, whereas bulk grains were studied after conventional tensile testing. The evolution of the deformation structure in surface and bulk grains displays a strong resemblance but the strain needed to obtain a similar deformation structure is lower in the case of surface grains. Both slip and twinning are observed to be important deformation mechanisms, whereas deformation-induced martensite formation is of minor importance. Since the stacking fault energy (SFE) is low, ~17 mJ/m2, dynamic recovery by cross slip of un-dissociated dislocations is unfavorable. This reduces the annihilation of dislocations which in turn leads to a significant increase of low angle boundaries with increasing strain. The low SFE also favors formation of deformation twins which reduces the slip distance, leading to a hardening similar to the Hall-Petch relation. The combination of a low ability for cross-slip and a reduced slip distance caused by twinning is concluded to be the main reason for maintaining a high strain-hardening rate up to strains close to necking.

  • 39.
    Yvell, Karin
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Grehk, T. M.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Microstructure characterization of 316L deformed at high strain rates using EBSD2016In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 122, p. 14-21Article in journal (Refereed)
    Abstract [en]

    Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s− 1 at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneous and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain.

  • 40.
    Yvell, Karin
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Grehk, T. M.
    Hedström, P.
    Borgenstam, A.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    EBSD analysis of surface and bulk microstructure evolution during interrupted tensile testing of a Fe-19Cr-12Ni alloy2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 141, p. 8-18Article in journal (Refereed)
    Abstract [en]

    Abstract The microstructure evolution in both surface and bulk grains in a pure Fe-19Cr-12Ni alloy has been analyzed using electron backscatter diffraction after tensile testing interrupted at different strains. Surface grains were studied during in situ tensile testing performed in a scanning electron microscope, whereas bulk grains were studied after conventional tensile testing. The evolution of the deformation structure in surface and bulk grains displays a strong resemblance but the strain needed to obtain a similar deformation structure is lower in the case of surface grains. Both slip and twinning are observed to be important deformation mechanisms, whereas deformation-induced martensite formation is of minor importance. Since the stacking fault energy (SFE) is low, 17mJ/m2, dynamic recovery by cross slip of un-dissociated dislocations is unfavorable. This reduces the annihilation of dislocations which in turn leads to a significant increase of low angle boundaries with increasing strain. The low SFE also favors formation of deformation twins which reduces the slip distance, leading to a hardening similar to the Hall-Petch relation. The combination of a low ability for cross-slip and a reduced slip distance caused by twinning is concluded to be the main reason for maintaining a high strain-hardening rate up to strains close to necking.

  • 41.
    Yvell, Karin
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Grehk, T. M.
    Hedström, P.
    Borgenstam, A.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Microstructure development in a high-nickel austenitic stainless steel using EBSD during in situ tensile deformation2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 135, no Supplement C, p. 228-237Article in journal (Refereed)
    Abstract [en]

    Plastic deformation of surface grains has been observed by electron backscatter diffraction technique during in situ tensile testing of a high-nickel austenitic stainless steel. The evolution of low- and high-angle boundaries as well as the orientation changes within individual grains has been studied. The number of low-angle boundaries and their respective misorientation increases with increasing strain and some of them also evolve into high-angle boundaries leading to grain fragmentation. The annealing twin boundaries successively lose their integrity with increasing strain. The changes in individual grains are characterized by an increasing spread of orientations and by grains moving towards more stable orientations with 〈111〉 or 〈001〉 parallel to the tensile direction. No deformation twins were observed and deformation was assumed to be caused by dislocation slip only.

  • 42.
    Yvell, Karin
    et al.
    Materials Science, Dalarna University, Falun, Sweden.
    Grehk, T. M.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Borgenstam, Annika
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Engberg, G.
    Microstructure development in a high-nickel austenitic stainless steel using EBSD during in situ tensile deformation2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 135, p. 228-237Article in journal (Refereed)
    Abstract [en]

    Plastic deformation of surface grains has been observed by electron backscatter diffraction technique during in situ tensile testing of a high-nickel austenitic stainless steel. The evolution of low- and high-angle boundaries as well as the orientation changes within individual grains has been studied. The number of low-angle boundaries and their respective misorientation increases with increasing strain and some of them also evolve into high-angle boundaries leading to grain fragmentation. The annealing twin boundaries successively lose their integrity with increasing strain. The changes in individual grains are characterized by an increasing spread of orientations and by grains moving towards more stable orientations with < 111 > or < 001 > parallel to the tensile direction. No deformation twins were observed and deformation was assumed to be caused by dislocation slip only.

  • 43.
    Åkerfeldt, Pia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hörnqvist Colliander, Magnus
    Department of Physics, Chalmers University of Technology.
    Pederson, Robert
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Engineering Science, University West.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Electron backscatter diffraction characterization of fatigue crack growth in laser metal wire deposited Ti-6Al-4V2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 135, p. 245-256Article in journal (Refereed)
    Abstract [en]

    By additive manufacturing (AM) there is a feasibility of producing near net shape components in basically one step from 3D CAD model to final product. The interest for AM is high and during the past decade a lot of research has been carried out in order to understand the influence from process parameters on the microstructure and furthermore on the mechanical properties. In the present study laser metal wire deposition of Ti-6Al-4V has been studied in detail with regard to its fatigue crack propagation characteristics. Two specimen orientations, parallel and perpendicular to the deposition direction, have been evaluated at room temperature and at 250 °C. No difference in the fatigue crack growth rate could be confirmed for the two specimen orientations. However, in the fractographic study it was observed that the tortuosity varied between certain regions on the fracture surface. The local crack path characteristic could be related to the alpha colony size and/or the crystallographic orientation. Moreover, large areas exhibiting similar crystallographic orientation were observed along the prior beta grain boundaries, which were attributed to the wide alpha colonies frequently observed along the prior beta grain boundaries.

  • 44.
    Åkerfeldt, Pia
    et al.
    Luleå University of Technology,Division of Materials Science, Luleå, Sweden.
    Hörnqvist Colliander, Magnus
    Chalmers University of Technology, Department of Physics, Göteborg, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology. Luleå University of Technology,Division of Materials Science, Luleå, Sweden.
    Antti, Marta-Lena
    Luleå University of Technology,Division of Materials Science, Luleå, Sweden.
    Electron backscatter diffraction characterization of fatigue crack growth in laser metal wire deposited Ti-6Al-4V2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 135, p. 245-256Article in journal (Refereed)
    Abstract [en]

    By additive manufacturing (AM) there is a feasibility of producing near net shape components in basically one step from 3D CAD model to final product. The interest for AM is high and during the past decade a lot of research has been carried out in order to understand the influence from process parameters on the microstructure and furthermore on the mechanical properties. In the present study laser metal wire deposition of Ti-6Al-4V has been studied in detail with regard to its fatigue crack propagation characteristics. Two specimen orientations, parallel and perpendicular to the deposition direction, have been evaluated at room temperature and at 250 °C. No difference in the fatigue crack growth rate could be confirmed for the two specimen orientations. However, in the fractographic study it was observed that the tortuosity varied between certain regions on the fracture surface. The local crack path characteristic could be related to the alpha colony size and/or the crystallographic orientation. Moreover, large areas exhibiting similar crystallographic orientation were observed along the prior beta grain boundaries, which were attributed to the wide alpha colonies frequently observed along the prior beta grain boundaries. © 2017 Elsevier Inc.

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