立方相MgSc合金力学性质的计算研究

Computational Study on the Mechanical Property of Cubic Phase MgSc Alloys

采用严格糕模轨道方法结合相干势近似计算,研究Mg_(1-x)Sc_(x)(0.10<x<0.25)合金立方晶格β相和γ相结构的力学性质。结果表明:Mg_(1-x)Sc_(x)(0.10<x<0.25)合金两种立方相的晶格常数、体积模量和弹性常数随着Sc组分的增加而增加。γ相的四方剪切模量C'>0,即此相在力学上是稳定的。γ相的弹性系数和体模量小于β相,但呈现的韧性优于β相。电子结构计算表明,基于正则能带理论的力定理不能解释γ相和β相单晶弹性常数的大小关系,而Sc合金化和电荷转移引入的马德隆相互作用对合金相稳定性和力学性质起关键作用。

The mechanical property ofβ-phase andγ-phase Mg_(1-x)Sc_(x)(0.10<x<0.25)alloys was investigated by exact muffin-tin orbital method in combination with coherent potential approximation.The calculated results indicated that the lattice constant,bulk modulus,elastic constants of Mg_(1-x)Sc_(x) in different phases increased with the increase of Sc concentration;the tetragonal shear modulus ofγ-phase was small but kept positive,and therefore,theγ-phase was mechanically stable;the elastic modulus ofγ-phase was smaller than that ofβ-phase,but the ductility ofγ-phase was better than that ofβ-phase.The electronic structure analysis demonstrated that the relative value of elastic constant forβ-phase andγ-phase was unaccountable by force theorem;however,the Madelung interaction induced by Sc alloying and charge transfer was playing pivotal key role on phase stability and mechanical properties of MgSc alloys.