摘要
为了研究稀土元素对镁锌合金性能的影响,利用基于第一性原理计算的平面波赝势方法,对Mg_2Y、Mg_2La和Mg_3La的结构稳定性、电子结构和力学性能进行了计算和分析。形成热和结合能的计算结果表明,Mg_3La具有最强合金化能力,而Mg_2La具有最强的结构稳定性。通过电子态密度(DOS),电子占据数和差分电荷密度分析了结构的稳定机制。计算了3种结构的弹性常数,并进一步得到了体模量B,剪切模量G,杨氏模量E和泊松比γ等。计算结果表明:Mg_2Y具有最强的抵抗变形能力,Mg_3La具有最强的刚度和抵抗剪切变形能力,而Mg_2La塑性最强。进一步分析表明Mg_2Y和Mg_2La为延性相,而Mg_3La为脆性相。此外,硬度和熔点的计算结果表明,3种金属间化合物中,Mg_3La的硬度最大,Mg_2Y的熔点最高。
In order to investigate the effect of rare earth elements on the properties of Mg-Zn magnesium alloys, the structural stability, electronic structure and mechanical properties of Mg_2Y, Mg_2La and Mg_3La compounds were calculated and analyzed by using the plane wave pseudo-potential method based on the first principles calculation. The results show that Mg_3La has the strongest forming ability, Mg_2La has the most stable structure by comparing the heat of formation and cohesive energy among the three compounds. The stabilization mechanism of the structure was analyzed based on the calculation of electron densities of states(DOS), electron occupation number and electron density difference. The bulk modulus B, shear modulus G, Young's modulus E, and Poisson's ratio v were further calculated by the elastic constants. The calculated results indicate that Mg_2Y has the strongest ability of resisting deformation, Mg_3La has the strongest stiffness and resistance to shear deformation, Mg_2La has the strongest plasticity, Mg_2Y and Mg_2La are ductile phases while Mg_3La is a brittle phase. In addition, the calculated results of hardness and melting temperature show that Mg_3La has the largest hardness and Mg_2Y has the highest melting temperature among the three compounds.
引文
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