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| 1 | The effect of Co and Cr substitutions for Ni on mechanical properties and plastic deformation mechanism of FeMnCoCrNi high entropy alloys显示文摘The elastic constants,ideal tensile strength(ITS),stacking fault energy(SFE),lattice constant and magnetic moment of FeMnCoCrNi high entropy alloys with varying Co and Cr contents at 0 and 300 K were systematically investigated by first-principle calculations.For the alloys with Co substitution for Ni,at both temperatures the elastic stability of the face-centered cubic(fcc)phase,bulk elastic modulus(B),Young’s modulus(E),shear modulus(G)and ITS increase monotonically with increasing Co content.However,the Cauchy pressure(Cp),Pugh ratio(B/G),Poisson ratio(v),Zener anisotropy ratio(AZ)and elastic anisotropy ratio(AVR)decrease monotonically.The SFE also decreases with the increase of Co,resulting in the change of plastic deformation mechanism from dislocation slip to mechanical twinning,and then to hcp-martensitic transformation.This elucidates the underlying mechanism of the effect of Co addition on the strength and micromechanical behavior of FeMnCoCrNi alloys.Compared with Co,the Cr substitution for Ni leads to the more complex change of elastic constants and ITS.The increase of Cr shows the similar effect on SFE and deformation mechanism as that of Co.The variation of valence electron concentration and magnetism affect the SFE.The increase of either Co or Cr leads to the reduced magnetic moments of Fe and Mn.This could be responsible for the monotonic decrease of both lattice constant and SFE as the Co content increases.However,for the Cr addition case,multiple factors may affect the evolution of lattice constant and SFE.These findings shed light on the deformation mechanism of the alloys with different compositions. | H.F.Zhang H.L.Yan H.Yu Z.W.Ji Q.M.Hu N.Jia | 2020 | Journal of Materials Science & Technology2020，47，13： | 5 |
| 2 | Solid solution strengthening of high-entropy alloys from first-principles study显示文摘Solid solution strengthening(SSS)is one kind of strengthening mechanisms and plays an important role in alloy design,in particular for single-phase alloys including high-entropy alloys(HEAs).The classical Labusch–Nabarro model and its expansions are most widely applicable to treating SSS of solid solution alloys including both conventional alloys(CAs)and HEAs.In this study,the SSS effects in a series of Febased CAs and HEAs are investigated by using the classical Labusch–Nabarro model and its expansions.The size misfit and shear modulus misfit parameters are derived from first-principles calculations.Based on available experimental data in combination with empirical SSS model,we propose fitting constants(i.e.,the ratio between experimental hardness and predicted SSS effect)for these two families of alloys.The predicted host/alloy family-dependent fitting constants can be used to estimate the hardness of these SSS alloys.General agreement between predicted and measured hardness values is satisfactory for both CAs and HEAs,implying that the proposed approach is reliable and successful. | H.L.Zhang D.D.Cai X.Sun H.Huang S.Lu Y.Z.Wang Q.M.Hu L.Vitos X.D.Ding | 2022 | Journal of Materials Science & Technology2022，，26： | 1 |
| 3 | Design and optimization of the composition and mechanical properties for non-equiatomic CoCrNi medium-entropy alloys显示文摘The development of multi-principal element alloys(MPEAs,also called as high-or medium-entropy al-loys,HEAs/MEAs)provides tremendous possibilities for materials innovation.However,designing MPEAs with desirable mechanical properties confronts great challenges due to their vast composition space.In this work,we provide an essential criterion to efficiently screen the CoCrNi MEAs with outstanding strength-ductility combinations.The negative Gibbs free energy difference△E_(FCC-BCC)between the face-centered cubic(FCC)and body-centered cubic(BCC)phases,the enhancement of shear modulus G and the decline of stacking fault energy(SFE)γ_(isf)are combined as three requisites to improve the FCC phase stability,yield strength,deformation mechanisms,work-hardening ability and ductility in the criterion.The effects of chemical composition on△E_(FCC-BCC),G andγisf were investigated with the first principles calculations for Co_(x)Cr_(33)Ni_(67-x),Co_(33)Cr_(y)Ni_(67-y)and Co_(z)Cr_(66-z)Ni_(34)(0≤x,y≤67 and 0≤z≤66)alloys.Based on the essential criterion and the calculation results,the composition space that displays the neg-ative Gibbs free energy difference△E_(FCC-BCC),highest shear modulus G and lowest SFEγ_(isf)was screened with the target on the combination of high strength and excellent ductility.In this context,the optimal composition space of Co-Cr-Ni alloys was predicted as 60 at.%-67 at.%Co,30 at.%-35 at.%Cr and 0 at.%-6 at.%Ni,which coincides well with the previous experimental evidence for Co_(55)Cr_(40)Ni_(5)alloys.The valid-ity of essential criterion is further proved after systematic comparison with numerous experimental data,which demonstrates that the essential criterion can provide significant guidance for the quick exploitation of strong and ductile MEAs and promote the development and application of MPEAs. | J.X.Yan Z.J.Zhang P.Zhang J.H.Liu H.Yu Q.M.Hu J.B.Yang Z.F.Zhang | 2023 | Journal of Materials Science & Technology2023，，8： | 0 |
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