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1.
  • Borgenstam, Annika, et al. (author)
  • Model for nucleation of isothermal martensite
  • 2001
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 45:8, s. 917-922
  • Journal article (peer-reviewed)abstract
    • Kaufman and Cohen's model for thermally activated growth of preexisting embroys of isothermal martensite was defined with a series of obstacles but they only considered jumps in one direction. Jumps in both directions across obstacles were recently considered and the activation energy for the net reaction was described. That nucleation model is now developed further.
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2.
  • Gouldstone, Andrew, et al. (author)
  • Onset of plastic yielding in thin metal lines deposited on substrates
  • 1999
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 41:3, s. 297-304
  • Journal article (peer-reviewed)abstract
    • A thermoelastic analysis of patterned lines on substrates to determine the critical conditions for the onset of yielding is investigated, which provides a new analytical tool for determining the yield properties of lines relative to those of films of the same thickness. Verification of the theory is provided with the aid of finite element simulations, and a method for experimentally extracting the plastic properties of lines is also outlined.
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3.
  • Hillert, M., et al. (author)
  • Comparison between solute drag and dissipation of Gibbs energy by diffusion
  • 2001
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 45:2, s. 221-227
  • Journal article (peer-reviewed)abstract
    • The solute drag and the dissipation of Gibbs energy in a partitionless phase transformation are compared numerically. They agree if the solute drag is compared with the driving force over the interface and the solute spike in front of the interface. The dissipation can be evaluated over this whole region or over the interface alone.
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4.
  • Hillert, Mats, et al. (author)
  • Discussion on local equilibrium at solid/liquid interfaces during melting
  • 2002
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 46:6, s. 455-457
  • Journal article (peer-reviewed)abstract
    • Melting experiments were recently used to support the assumption of considerable deviation from local equilibrium. It is now claimed that the observed velocities of melting were low enough to allow diffusion in the solid to give a well developed spike of the solute in front of the migrating interface making a strong deviation from local equilibrium unlikely.
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5.
  • Hillert, Mats (author)
  • Nature of local equilibrium at the interface in the growth of ferrite from alloyed austenite
  • 2002
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 46:6, s. 447-453
  • Journal article (peer-reviewed)abstract
    • The increase over the years of experimental information on the effect of alloying elements on the transformation of austenite to ferrite and of the theoretical understanding is reviewed. The prediction of two kinds of transitions in behavior is described and the importance of exploring them experimentally is stressed.
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6.
  • Hillert, Mats (author)
  • Paradigm shift for bainite
  • 2002
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 47:3, s. 175-180
  • Journal article (peer-reviewed)abstract
    • One of the pictures of the mechanism of the bainitic transformation has been based upon the paradigm that it is closely related to the martensitic transformation. It has resulted in an unjustified belief in high growth velocity and high supersaturation of carbon in bainitic ferrite. It seems that the time is now right for abandoning that paradigm.
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7.
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8.
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9.
  • Larsson, Henrik, et al. (author)
  • A random-walk approach to diffusion controlled growth
  • 2003
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 49:6, s. 521-526
  • Journal article (peer-reviewed)abstract
    • The new method does not require formulation of any special conditions at the moving phase interface. Although only binary systems are treated at present an extension to any number of components seems straightforward. A good agreement with conventional front tracking techniques (DICTRA) is found.
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10.
  • Molina-Aldareguia, J.M., et al. (author)
  • Kink formation around indents in laminated Ti3SiC2 thin films studied in the nanoscale
  • 2003
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 49:2, s. 155-160
  • Journal article (peer-reviewed)abstract
    • The deformation mechanisms in ductile Ti3SiC2(0 0 0 1) single-crystal films have been analysed by nanoindentation and cross-sectional transmission electron microscopy. Permanent deformation includes formation of kink bands, as the nanolaminated material buckles out at the perimeter of the contact area, and delamination cracks. Evidence is presented for incipient kink-band formation.
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11.
  • Panagopoulos, C.N., et al. (author)
  • Ni-P-W multilayered alloy coatings produced by pulse plating
  • 2000
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 43:7, s. 677-683
  • Journal article (peer-reviewed)abstract
    • The possibility of producing multilayered alloy coatings consisting of alternate amorphous layers, by the electrodeposition method, using pulsed current was investigated. The alternate metallic amorphous layers were selected to consist of Ni-P-W ternary alloys, in order to study the effect of the incorporation of a third element in the structure of an electrodeposited Ni-P multilayered alloy coating. The well-defined layered structure found in the Ni-P-W multilayered alloy coatings, consisting of X-ray amorphous layers, shows that production of a ternary Ni-P-W multilayered alloy coating with the selected method is feasible and this may expand the potential applications of a Ni-P based multilayered alloy coating.
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12.
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13.
  • Ågren, John (author)
  • On the classification of phase transformations
  • 2002
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 46:12, s. 893-898
  • Journal article (peer-reviewed)abstract
    • The various classification schemes, based on thermodynamics, microstructure or mechanism, are discussed and criticized from a practical as well as a more fundamental point of view. For example, it is generally not meaningful to consider first and second-order transformations as equivalent with heterogeneous and homogeneous transformations, respectively.
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14.
  • Ananthanarayanan, Durga, et al. (author)
  • Grain refinement in additively manufactured ferritic stainless steel by in situ inoculation using pre-alloyed powder
  • 2021
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 194
  • Journal article (peer-reviewed)abstract
    • For ferritic stainless steels, TiN has effectively been used as an inoculant to produce equiaxed grain structures in casting and welding. However, it is not established whether TiN would be an effective inoculant in additive manufacturing. In this study, the effectiveness of TiN as an inoculant in a ferritic stainless steel processed by laser powder-bed fusion is studied. An alloy without Ti is fabricated and compared to an alloy designed to form a high amount of TiN early during solidification. The work shows that the presence of TiN provides general grain refinement and that TiN-covered oxide particles are effective in enabling columnar-to-equiaxed transition in certain regions of the meltpool. The applied approach of pre-alloying powders with inoculant-forming elements offers a straightforward route to achieving fine, equiaxed grain structures in additively manufactured metallic materials. It also shows how oxygen present during the process can be utilized to nucleate effective inoculating phases.
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15.
  • Anasori, Babak, et al. (author)
  • Mo2TiAlC2: A new ordered layered ternary carbide
  • 2015
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 101, s. 5-7
  • Journal article (peer-reviewed)abstract
    • Herein we report on the synthesis of a new layered ternary carbide, Mo2TiAlC2, that was synthesized by heating an elemental mixture at 1600 degrees C for 4 h under an Ar flow. Its hexagonal, a and c lattice parameters were calculated via Rietveld analysis of powder X-ray diffraction patterns to be, respectively, 2.997 angstrom and 18.661 angstrom. High-resolution scanning transmission electron microscopy showed that this phase is ordered, with Ti layers sandwiched between two Mo layers in a M(3)AX(2) type ternary carbide structure. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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16.
  • Asp Grönhagen, Klara, et al. (author)
  • Phase-field modelling of spinodal decomposition in TiAlN including the effect of metal vacancies
  • 2015
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 95, s. 42-45
  • Journal article (peer-reviewed)abstract
    • Using a CALPHAD approach together with a Cahn-Hilliard model, we describe the microstructure evolution in cubic Ti1-xAlxN including vacancies on the metal sublattice. Our results show that vacancy content has a pronounced effect on the decomposition kinetics. Furthermore, vacancies show a strong tendency to segregate to the coherent AlN-TiN interface regions. We illustrate how vacancies anneal to grain boundaries, and finally, we compare our prediction to experimental differential scanning calorimetry data and attribute the second peak in the thermogram to vacancy depletion.
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17.
  • Bakhit, Babak, 1983-, et al. (author)
  • Age hardening in superhard ZrB2-rich Zr1-xTaxBy thin films
  • 2021
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 191, s. 120-125
  • Journal article (peer-reviewed)abstract
    • We recently showed that sputter-deposited Zr1-xTaxBy thin films have hexagonal AlB2-type columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. As-deposited layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we study the mechanical properties of ZrB2.4, Zr0.8Ta0.2B1.8, and Zr0.7Ta0.3B1.5 films annealed in Ar atmosphere as a function of annealing temperature Ta up to 1200 °C. In-situ and ex-situ nanoindentation analyses reveal that all films undergo age hardening up to Ta = 800 °C, with the highest hardness achieved for Zr0.8Ta0.2B1.8 (45.5±1.0 GPa). The age hardening, which occurs without any phase separation or decomposition, can be explained by point-defect recovery that enhances chemical bond density. Although hardness decreases at Ta > 800 °C due mainly to recrystallization, column coarsening, and planar defect annihilation, all layers show hardness values above 34 GPa over the entire Ta range.
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18.
  • Barnett, M.R., et al. (author)
  • Role of grain boundary sliding in the anisotropy of magnesium alloys
  • 2009
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 61:3, s. 277-280
  • Journal article (peer-reviewed)abstract
    • The plastic anisotropy of magnesium alloy sheet drops rapidly with test temperature. It has previously been suggested that this may be due to an increase in the activity of 〈c+a〉 dislocations. The present note points out that the phenomenon may result, instead, from the action of grain boundary sliding. This can explain the strong effect of grain size on anisotropy. Furthermore, it points to a new avenue for alloy development. © 2009 Acta Materialia Inc.
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19.
  • Barrirero, Jenifer, et al. (author)
  • Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys
  • 2016
  • In: Scripta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6462 .- 1872-8456. ; 117, s. 16-19
  • Journal article (peer-reviewed)abstract
    • Atom probe tomography was used to compare Na and Sr modified Al-Si hypoeutectic alloys. Both Na and Sr promote the formation of nanometre-sized clusters in the Si eutectic phase. Compositional analyses of the clusters show an Al:Sr ratio of 2.92 +/- 0.46 and an Al:Na ratio of 1.07 +/- 0.23. It is proposed that SrAl2Si2 and NaAlSi clusters are formed at the Si/liquid interface and take part in the modification process by altering the eutectic Si growth.
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20.
  • Bartosik, M., et al. (author)
  • Interface controlled microstructure evolution in nanolayered thin films
  • 2016
  • In: Scripta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6462 .- 1872-8456. ; 123, s. 13-16
  • Journal article (peer-reviewed)abstract
    • X-ray nano-diffraction and transmission electron microscopy were conducted along the thickness of a similar to 4 pm thick CrN/AlN multilayer with continuously increasing AlN layer thicknesses from similar to 1 to 15 nm on similar to 7 nm thick CrN template layers. The experiments reveal coherent growth, large columnar grains extending over several (bi-)layers for thin AlN layer thicknesses below similar to 4 nm. Above similar to 4 nm, the nucleation of the thermodynamically stable wurtzite structured AlN is favored, leading to coherency breakdown and reduction of the overall strains, disrupting the columnar microstructure and limiting the maximum grain size in film growth direction to the layer thickness. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd.
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21.
  • Basu, A., et al. (author)
  • Laser surface hardening of austempered (bainitic) ball bearing steel
  • 2007
  • In: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 56:10, s. 887-890
  • Journal article (peer-reviewed)abstract
    • This study concerns laser surface hardening (LSH) of austempered SAE 52100 steel to enhance hardness and wear resistance. Following LSH with selected laser parameters, surface microstructure and mechanical properties were evaluated by optical/scanning electron microscopy, X-ray diffraction, hardness measurement and wear studies, and thermal profile modeling. The results suggest that LSH could develop residual compressive stress and high hardness and wear resistance in this steel without affecting the bainitic core. © 2007 Acta Materialia Inc.
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22.
  • Baykov, Vitaly, et al. (author)
  • Structural stability of intermetallic phases in the Zr-Sn system
  • 2006
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 55:5, s. 485-488
  • Journal article (peer-reviewed)abstract
    • 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.
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23.
  • Bernard-Granger, G., et al. (author)
  • Influence of graphite contamination on the optical properties of transparent spinel obtained by spark plasma sintering
  • 2009
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 60:3, s. 164-167
  • Journal article (peer-reviewed)abstract
    • The optical properties of transparent spinel sintered by spark plasma sintering have been investigated for incident electromagnetic radiations with wavelengths in the range 0.2-2 mu m. It is shown that residual porosities and second-phase graphite particles have a strong influence on the in-line transmittance. Because of the graphite particles, the in-line transmittance measured does not approach that of monocrystalline spinel for wavelengths above 1 mu m. 
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24.
  • Broitman, Esteban, et al. (author)
  • High-temperature nanoindentation of epitaxial ZrB2 thin films
  • 2016
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 124, s. 117-120
  • Journal article (peer-reviewed)abstract
    • We use in-situ heated nanoindentation to investigate the high-temperature nanomechanical properties of epitaxial and textured ZrB2 films deposited by magnetron sputtering. Epitaxial films deposited on 4H-SiC(0001) show a hardness decrease from 47 GPa at room temperature to 33 GPa at 600 °C, while the reduced elastic modulus does not change significantly. High resolution electron microscopy (HRTEM) with selected area electron diffraction of the indented area in a 0001-textured film reveals a retained continuous ZrB2 film and no sign of crystalline phase transformation, despite massive deformation of the Si substrate. HRTEM analysis supports the high elastic recovery of 96% in the films.
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25.
  • Bu, Junfu, et al. (author)
  • Dense and translucent BaZrxCe0.8-xY0.2O3-delta (x=0.5, 0.6, 0.7) proton conductors prepared by spark plasma sintering
  • 2015
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 107, s. 145-148
  • Journal article (peer-reviewed)abstract
    • Dense and translucent BaZrxCe0.8-xY0.2O3-delta (x = 0.5, 0.6, 0.7) proton conductors were firstly and successfully prepared by Spark Plasma Sintering (SPS) at a temperature of 1350 degrees C without sintering aids' addition. XRD, SEM and EDS were applied to determine the phase purity, morphology and element composition of prepared pellets, respectively. Moreover, the sintering behaviors of these proton conductors were monitored and analyzed through the on-line sintering curves. The obtained results indicate that a lowered sintering temperature (<1400 degrees C) and a fast cooling rate (>= 200 degrees C/min) represent two key parameters to prepare dense Ce-containing BaZrO3-BaCeO3 based proton conductors.
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26.
  • Bu, Junfu, et al. (author)
  • Electrical conductivities of translucent BaZr(X)Ce0.8-XY0.2O3-delta (x=0.5, 0.6, 0.7) ceramics
  • 2016
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 115, s. 87-90
  • Journal article (peer-reviewed)abstract
    • The electrical conductivities of translucent BaZr0.5Ce0.3Y0.2O3-delta (x = 0.5, BZCY532), BaZr0.6Ce0.2Y0.2O3-delta (x = 0.6, BZCY622) and BaZr0.7Ce0.1Y0.2O3-delta(x = 0.7, BZCY712) proton conductors were investigated systematically in different atmospheres and also at different oxygen partial pressures. The obtained results indicate that translucent BZCY532, BZCY622 and BZCY712 ceramics are pure oxygen-ion and proton conductors without unfavorable electronic conduction. In addition, they represent promising proton conductors to be used as intermediate temperature solid oxide fuel cell electrolytes.
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27.
  • Chai, Guocai, et al. (author)
  • Local Plasticity Exhaustion in a Very High Cycle Fatigue Regime
  • 2012
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 66:10, s. 769-772
  • Journal article (peer-reviewed)abstract
    • Very high cycle fatigue behaviors of four metal materials with different microstructures have been studied focusing on their damage mechanisms. It was found that the cyclic plastic deformation in the materials was highly localized in the very high cycle regime or the elastic deformation regime. This high strain localization can cause local plasticity exhaustion, which leads to a stress concentration and consequently fatigue crack initation, and finally the formation of a subsurface non-defect fatigue crack origin.
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28.
  • Chen, Kaixuan, et al. (author)
  • Mapping formation mechanisms and transformation regimes of multiple Fe precipitates in Cu-Fe-Co alloy during casting process
  • 2024
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 246
  • Journal article (peer-reviewed)abstract
    • Precipitate features including size, morphology, crystal structure, etc., are important parameters determining the performance of precipitate-strengthened alloys. Multiple Fe precipitates were identified in as-cast Cu alloys exhibiting the distinct features, which dramatically influence mechanical properties. However, a complete understanding of precipitation behaviors of Fe particles during casting, in terms of both microscopic kinetics and thermodynamics, remains experimentally challenging. Here, we report the combined implementation of transmission electron microscopy, Thermo-Calc calculations and First-principles calculations to map mechanisms and growth regimes of Fe precipitation in a Cu-Fe-Co system. Our analyses support the idea that to understand the microstructural evolution in the system, both thermodynamic and kinetic arguments must be taken into account. Then, using our multi-approach strategy, the complete picture of the formation and transformation of Fe precipitates is proposed. This work is vital to promote microstructural design for Cu-Fe(-Co) systems, and sheds new insights into understanding of intricate precipitation in alloys.
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29.
  • Cheng, Q., et al. (author)
  • Solid solution softening in a Aloi CoCrFeMnNi high-entropy alloy
  • 2020
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 186, s. 63-68
  • Journal article (peer-reviewed)abstract
    • Solute effects on high-entropy alloys of equiatomic proportions are scientifically intriguing because there is no such well-defined "solute" and "solvent" atoms compared to those of conventional single principal element alloys. To date, most of the face-centered cubic alloys exhibit solid solution strengthening rather than softening due to the interactions between dislocations and solute atoms. Here, we present the careful experimental measurements and demonstrate solid solution softening, albeit weak, in a single phase CoCrFeMnNi through the minor addition of 2. at.% Al. This softening effect is mostly related to the decreased Peierl's stress by Al addition.
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30.
  • Ciudad, Esther, et al. (author)
  • Sliding-wear resistance of ultrafine-grained SiC densified by spark plasma sintering with 3Y(2)O(3)+5Al(2)O(3) or Y3Al5O12 additives
  • 2013
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 69:8, s. 598-601
  • Journal article (peer-reviewed)abstract
    • The sliding-wear behavior of ultrafine-grained SiC densified by spark plasma sintering (SPS) with 3Y(2)O(3) + 5Al(2)O(3) or Y3Al5O12 additives was compared to elucidate the effect of the intergranular-phase source. Significantly greater sliding-wear resistance (i.e. lower mild- and severe-wear rates, and delayed mild-to-severe wear transition) is observed with the Y3Al5O12 additive, due to its carbothermal reduction during SPS resulting in a harder YAlO3 phase while reducing the intergranular phase content. Implications for the processing of superior SiC triboceramics are discussed.
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31.
  • Cui, Luqing, et al. (author)
  • Cyclic Response of Additive Manufactured 316L Stainless Steel : The Role of Cell Structures
  • 2021
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 205
  • Journal article (peer-reviewed)abstract
    • We report the effect of cell structures on the fatigue behavior of additively manufactured (AM) 316L stainless steel (316LSS). Compared with the cell-free samples, the fatigue process of fully cellular samples only consists of steady and overload stages, without an initial softening stage. Moreover, the fully cellular sample possesses higher strength, lower cyclic softening rate and longer lifetime. Microscopic analyses show no difference in grain orientations, dimensions, and shapes. However, the fully cellular samples show planar dislocation structures, whereas the cell-free samples display wavy dislocation structures. The existence of cell structures promotes the activation of planar slip, delays strain localization, and ultimately enhances the fatigue performance of AM 316LSS.
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32.
  • Dahlström, Alexander, et al. (author)
  • Nanostructure in Fe0.65Cr0.35 close to the upper limit of the miscibility gap
  • 2020
  • In: Scripta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6462 .- 1872-8456. ; 180, s. 62-65
  • Journal article (peer-reviewed)abstract
    • The nanostructure of an Fe0.65Cr0.35 alloy has been investigated by atom probe tomography after high precision thermal treatments close to the upper limit of the miscibility gap (MG). It is found that the wavelength of the decomposed ferrite between Cr- and Fe-rich regions grows exponentially when approaching the upper limit of the MG. Furthermore, the nanostructure change is gradual with temperature indicating a narrow metastable region and a diffuse transition out of the spinodal regime. Atomistic modelling near the limit of instability further supports the experimental observations. The findings are discussed in relation to the Cahn-Hilliard theory.
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33.
  • Delczeg-Czirjak, Erna K., et al. (author)
  • The effect of longitudinal spin-fluctuations on high temperature properties of Co3Mn2Ge
  • 2023
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 226
  • Journal article (peer-reviewed)abstract
    • It is demonstrated that thermally induced longitudinal spin fluctuations (LSF) play an important role in itinerant Co3Mn2Ge at an elevated temperature. The effect of LSF is taken into account during ab initio calculations via a simple model for the corresponding entropy contribution. We show that the magnetic entropy leads to the appearance of a medium size local moment on Co atoms. As a consequence, this leads to a renormalization of the magnetic exchange interactions with a quite substantial impact upon the calculated Curie temperature. Taking LSF into account, the calculated Curie temperature can be brought to be in good agreement with the experimental value.
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34.
  • Ding, Yu, et al. (author)
  • Hydrogen-induced transgranular to intergranular fracture transition in bi-crystalline nickel
  • 2021
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 204
  • Journal article (peer-reviewed)abstract
    • It is known that hydrogen can influence the dislocation plasticity and fracture mode transition of metallic materials, however, the nanoscale interaction mechanism between hydrogen and grain boundary largely remains illusive. By uniaxial straining of bi-crystalline Ni with a Σ5(210)[001] grain boundary, a transgranular to intergranular fracture transition facilitated by hydrogen is elucidated by atomistic modeling, and a specific hydrogen-controlled plasticity mechanism is revealed. Hydrogen is found to form a local atmosphere in the vicinity of grain boundary, which induces a local stress concentration and inhibits the subsequent stress relaxation at the grain boundary during deformation. It is this local stress concentration that promotes earlier dislocation emission, twinning evolution, and generation of more vacancies that facilitate nanovoiding. The nucleation and growth of nanovoids finally leads to intergranular fracture at the grain boundary, in contrast to the transgranular fracture of hydrogen-free sample.
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35.
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36.
  • Dominguez-Rodriguez, Arturo, et al. (author)
  • Making ceramics ductile at low homologous temperatures
  • 2007
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 56:2, s. 89-91
  • Journal article (peer-reviewed)abstract
    • Polycrystalline ceramics are brittle at room temperature but may deform by dislocation slip processes at higher temperatures, where T >= 0.5 T-M (T-M, the melting temperature), leading to strain hardening, i.e. the total strain to rupture is limited. We show that mutual sliding of nanometer grains and atomic transport along their boundaries enables low-temperature metal-like plasticity in nanocrystalline ceramics. Compression of fully dense MgO nanoceramics at temperatures as low as 700 degrees C (0.31 T-M) exhibited stress-strain curves with no strain hardening.
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37.
  • Dong, Zhihua, et al. (author)
  • Finite temperature magnetic properties of CrxCoyNi100-x-y medium entropy alloys from first principles
  • 2019
  • In: Scripta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6462 .- 1872-8456. ; 171, s. 78-82
  • Journal article (peer-reviewed)abstract
    • The magnetic structure of polymorphic Cr-Co-Ni medium entropy alloys is investigated as a function of temperature and chemical composition by ab initio calculations. Besides the thermal lattice expansion, the longitudinal spin fluctuations (LSFs) are accounted for in determining the magnetic state at finite temperature. We show that sizable local magnetic moments persist on all alloy components in the paramagnetic state for both face-centered cubic and hexagonal close-packed structures, and each alloy species exhibits particular temperature and concentration dependencies. The crucial role of LSFs for the finite temperature magnetic state and its impact on the temperature dependent elastic parameters are demonstrated.
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38.
  • Dong, Zhihua, et al. (author)
  • Strong temperature – Dependence of Ni -alloying influence on the stacking fault energy in austenitic stainless steel
  • 2020
  • In: Scripta Materialia. - : Acta Materialia Inc. - 1359-6462 .- 1872-8456. ; 178, s. 438-441
  • Journal article (peer-reviewed)abstract
    • Using ab initio alloy theory, we calculate the impact of Ni on the stacking fault energy in austenitic stainless steel as a function of temperature. We show that the influence of Ni strongly couples with temperature. While a positive effect on the stacking fault energy is obtained at ambient temperature, the opposite negative effect is disclosed at elevated temperatures. An important rationale behind is demonstrated to be the variation of magneto-volume coupling induced by Ni alloying. The alloy influence on the finite temperature evolution of Ni impact is evaluated for elements Cr, Mo and N.
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39.
  • Dorri, Megan, et al. (author)
  • Synthesis and characterization of CrB 2 thin films grown by DC magnetron sputtering
  • 2021
  • In: Scripta Materialia. - : Pergamon-Elsevier Science Ltd. - 1359-6462 .- 1872-8456. ; 200
  • Journal article (peer-reviewed)abstract
    • CrB x thin films with 1.90 < x < 2.08 have been deposited by direct-current magnetron sputtering (DCMS) from a stoichiometric CrB 2 target at 5 and 20 mTorr (0.67 and 2.67 Pa) Ar pressure onto sapphire (0 0 01) substrates. All films, irrespective of deposition conditions, exhibit a (0 0 01) texture. Attesting to the achievement of close-to-stoichiometric composition, epitaxial film growth is observed at 900 ?C, while film growth at 500 ?C yields (0001) fiber texture. Film composition does not depend on substrate temperature but exhibits slightly reduced B content with increasing pressure for samples deposited at 900 ?C. Excess B in the overstoichiometric epitaxial CrB 2.08 films segregates to form B-rich inclusions. Understoichiometry in CrB 1.90 films is accommodated by Cr-rich stacking faults on { 1 1? 00 } prismatic planes. ? 2021 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )
  •  
40.
  • Du, Hao, et al. (author)
  • Corundum-structured AlCrNbTi oxide film grown using high-energy early-arriving ion irradiation in high-power impulse magnetron sputtering
  • 2023
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 234
  • Journal article (peer-reviewed)abstract
    • Multicomponent or high-entropy oxide films are of interest due to their remarkable structure and properties. Here, energetic ion irradiation is utilized for controlling the phase formation and structure of AlCrNbTi oxide at growth temperature of 500 degrees C. The ion acceleration is achieved by using a high-power impulse magnetron sputtering (HiPIMS) discharge, accompanied by a 10 & mu;s-long synchronized substrate bias (Usync), to minimize the surface charging effect and accelerate early-arriving ions, mainly Al+, O+, Ar2+, and Al2+. By increasing the magnitude of Usync from-100 V to-500 V, the film structure changes from amorphous to single-phase corundum, followed by the formation of high-number-density stacking faults (or nanotwins) at Usync =-500 V. This approach paves the way to tailor the high-temperature-phase and defect formation of oxide films at low growth temperature, with prospects for use in protective-coating and dielectric applications.
  •  
41.
  • Edmondson, P. D., et al. (author)
  • Helium entrapment in a nanostructured ferritic alloy
  • 2011
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 65:8, s. 731-734
  • Journal article (peer-reviewed)abstract
    • A nanostructured ferritic alloy was irradiated with He+ to simulate service in a nuclear reactor and to test the hypothesis that the surface of nanoclusters is a preferential nucleation site for He bubbles. Transmission electron microscopy and atom probe tomography showed direct evidence of He bubble nucleation on the surfaces of nanoclusters and Ti(N,C) precipitates, and along grain boundaries and dislocations, thereby demonstrating an alloy design approach to improve the radiation tolerance of structural steels in the extreme environments found in nuclear reactors.
  •  
42.
  • Fashandi, Hossein, et al. (author)
  • Single-step synthesis process of Ti3SiC2 ohmic contacts on 4H-SiC by sputter-deposition of Ti
  • 2015
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 99, s. 53-56
  • Journal article (peer-reviewed)abstract
    • We report a single-step procedure for growth of ohmic Ti3SiC2 on 4H-SiC by sputter-deposition of Ti at 960 degrees C, based on the Ti-SiC solid-state reaction during deposition. X-ray diffraction and electron microscopy show the growth of interfacial Ti3SiC2. The as-deposited contacts are ohmic, in contrast to multistep processes with deposition followed by rapid thermal annealing. This procedure also offers the possibility of direct synthesis of oxygen-barrier capping layers before exposure to air, potentially improving contact stability in high-temperature and high-power devices.
  •  
43.
  • Ghassemali, Ehsan, 1983-, et al. (author)
  • Revisiting the graphite nodule in ductile iron
  • 2019
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 161, s. 66-69
  • Journal article (peer-reviewed)abstract
    • The growth mechanism of graphite nodules in ductile iron was experimentally investigated using high-resolution 3D tomography of an individual graphite nodule in a near-eutectic ductile iron. The dual beam scanning electron microscopy (FIB-SEM) technique was used for this purpose. Iron particles elongated in the radial direction were observed inside a graphite nodule. Some micro-voids were detected inside the nodule, mostly located at the end of the iron particles. These observations were compared with established theories about the growth of graphite nodules and iron entrapment/engulfment in between the graphite sectors during solidification of ductile iron. 
  •  
44.
  • Gorbatov, Oleg I., et al. (author)
  • Effect of Ni and Mn on the formation of Cu precipitates in α-Fe
  • 2015
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 102, s. 11-14
  • Journal article (peer-reviewed)abstract
    • Decomposition in bcc Fe-Cu-Ni and Fe-Cu-Mn alloys is studied using statistical thermodynamics simulations with ab initio effective interactions. It is demonstrated that magnetic state strongly affects the effective interactions in these systems, substantially increasing phase separation tendency with magnetization. Simulations show that Ni is promoting precipitation of Cu by segregating to the precipitate matrix interface, while Mn produces almost no effect distributing more homogeneously in the system. The obtained distributions of Ni and Mn are in good agreement with experimental data.
  •  
45.
  • Gorbatov, Oleg I., et al. (author)
  • Many-body mechanism of Guinier-Preston zones stabilization in Al–Cu alloys
  • 2017
  • In: Scripta Materialia. - : Acta Materialia Inc. - 1359-6462 .- 1872-8456. ; 138, s. 130-133
  • Journal article (peer-reviewed)abstract
    • Thermodynamics and atomic structures of pre-precipitates in dilute Al–Cu alloys are studied using Metropolis Monte Carlo simulations with many-body effective cluster interactions that have been systematically derived from ab initio supercell calculations. We show that many-body interactions, including the contributions due to lattice relaxations around the solute atoms, are mainly responsible for the formation of metastable planar atomic arrangements known as Guinier-Preston zones. Interaction terms up to four-body clusters are shown to be necessary to correctly reproduce the structures and temperatures of pre-precipitation in Al–Cu solid solutions.
  •  
46.
  • Greczynski, Grzegorz, et al. (author)
  • Nitrogen-doped bcc-Cr films: Combining ceramic hardness with metallic toughness and conductivity
  • 2016
  • In: Scripta Materialia. - : Elsevier Ltd. - 1359-6462 .- 1872-8456. ; 122, s. 40-44
  • Journal article (peer-reviewed)abstract
    • We report the first results on nanostructured N-doped bcc-Cr films exhibiting the unique combination of ceramic hardness with metallic toughness and electrical conductivity at unexpectedly low N concentrations, ~ 5 at.%. The Cr:N films are deposited at 200 C in N2/Ar mixtures by high-power pulsed magnetron sputtering using tunable time-domain control of Cr+ and Cr2+ ion fluxes incident at the film growth surface. Subplanted N atoms impede annealing of metal-ion induced point defects and hinder bcc-Cr grain growth, resulting in a material with a nearly isotropic nanostructure and atomically smooth surface, rather than typical Cr:N solid solutions consisting of faceted microcolumns. © 2016 Elsevier Ltd.
  •  
47.
  • Gu, Z. J., et al. (author)
  • Optimizing transformation-induced plasticity in CoCrNi alloys by combined grain refinement and chemical tuning
  • 2022
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 214, s. 114658-
  • Journal article (peer-reviewed)abstract
    • Grain refinement increases yield strength, but usually at the cost of ductility reduction. In the present work, we explored the strategy of grain refinement and composition tuning in CoCrNi alloys to optimize mechanical properties. Grain refinement was found to strongly suppress deformation-induced martensitic transformation in metastable CoCrNi alloys, which was utilized to modulate the transformation-induced plasticity (TRIP) effect in combination with composition tuning guided by theoretical calculations. We demonstrated in a non-equiatomic CoCrNi TRIP medium-entropy alloy (MEA) that our approach resulted in an excellent combination of strength and ductility. The proposed strategy is expected to be useful in exploring superior mechanical properties of MEAs and high-entropy alloys in varying systems.
  •  
48.
  • Hahn, R., et al. (author)
  • Unraveling the superlattice effect for hexagonal transition metal diboride coatings
  • 2023
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 235
  • Journal article (peer-reviewed)abstract
    • Superlattice structures enable the simultaneous enhancement in hardness (H) and fracture toughness (KIC) of ceramic-like coatings. While a deeper understanding of this effect has been gained for fcc-structured transition metal nitrides (TMN), hardly any knowledge is available for hexagonal diborides (TMB2). Here we show that superlattices can-similarly to nitrides-increase the hardness and toughness of diboride films. For this purpose, we deposited TiB2/WB2 and TiB2/ZrB2 superlattices with different bilayer periods (?) by non-reactive sputtering. Nanoindentation and in-situ microcantilever bending tests yield a distinct H peak for the TiB2/WB2 system (45.5 & PLUSMN; 1.3 GPa for ? = 6 nm) but no increase in KIC related to a difference in shear moduli (112 GPa). Contrary, the TiB2/ZrB2 system shows no peak in H, but for KIC with 3.70 & PLUSMN; 0.26 MPa & BULL;m1/2 at ? = 4 nm originating from differences in lattice spacing (0.14 & ANGS;), hence causing coherent stresses retarding crack growth.
  •  
49.
  • Hedlund, Daniel, et al. (author)
  • Influence of Mn content on the magnetic properties of the hexagonal Mn (Co,Ge)2 phase
  • 2023
  • In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 233
  • Journal article (peer-reviewed)abstract
    • Herein, we report on the effect of Mn content on the magnetic properties of the hexagonal Mn(Co,Ge)2 with composition Mn36+xCo49-xGe15.This compound was previously described as Mn2Co3Ge (MgZn2-type structure), but later as Mn(Co,Ge)2 with its own structure type, all samples in this work follow the same superstructure model. Samples were synthesized by induction melting, the crystal structures were evaluated using a combination of X-ray diffraction together with scanning electron microscopy equipped and an energy dispersive X-ray spectroscopy detector. The Curie temperature (TC) is shifted towards lower temperature as the Mn content is increased. On the other hand, the spin reorientation temperature (TSRT) increases and the magnetic moment decreases as the Mn content is increased. The magnetocaloric properties were investigated for the x = 1 alloy, Mn37Co48Ge15. It was found that the isothermal entropy change is 2 J kg−1 K−1 at room temperature for an applied field of 5 T.
  •  
50.
  • Hedström, Peter, et al. (author)
  • Stepwise transformation behavior of the strain-induced martensitic transformation in a metastable stainless steel
  • 2007
  • In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 56:3, s. 213-216
  • Journal article (peer-reviewed)abstract
    • In situ high-energy X-ray diffraction during tensile loading has been used to investigate the evolution of lattice strains and the accompanying strain-induced martensitic transformation in cold-rolled sheets of a metastable stainless steel. At high applied strains the transformation to α-martensite occurs in stepwise bursts. These stepwise transformation events are correlated with stepwise increased lattice strains and peak broadening in the austenite phase. The stepwise transformation arises from growth of α-martensite embryos by autocatalytic transformation.
  •  
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