材料期刊网

采用基于密度泛函理论的CASTEP和DMOL程序软件包, 计算了Mg₁₇Al₁₂, Al₂Sr和Mg₂Sr相的结构稳定性、弹性性能和电子结构. 合金形成热和结合能的计算结果显示, Al₂Sr具有最强的合金化形成能力和结构稳定性.Gibbs自由能的计算结果表明, 随着温度的升高, Mg₁₇Al₁₂, Al₂Sr和Mg₂Sr的结构稳定性发生了变化, 在实际工作温度高于423 K以上时,Al₂Sr的结构稳定性最好, Sr合金化Mg-Al基合金形成Al₂Sr有利于提高镁合金的高温抗蠕变性能. 体模量(B)、弹性各向异性系数(A)、Young's模量(E)、剪切模量(G)和Poisson比($\nu$)的计算结果表明, Mg₂Sr为延性相, 而Mg₁₇Al₁₂和Al₂Sr为脆性相, Mg₂Sr的塑性最好.态密度和Mulliken电子占据数的计算结果表明, Al₂Sr结构最稳定的原因主要源于体系存在强烈的共价键作用, 而Mg₁₇Al₁₂结构稳定性优于Mg₂Sr是体系中离子键与共价键共同作用的结果.

 Structural stabilities, elastic properties and electronic structures of Mg₁₇Al₁₂, Al₂Sr and Mg₂Sr phases have been determined from first–principle calculations by using CASTEP and DMOL programs based on the density functional theory. The calculated formation heats and cohesive energies indicated that Al₂Sr has the strongest alloying ability as well as the highest structural stability. The calculated Gibbs free energy showed that the structural stabilities of Mg₁₇Al₁₂, Al₂Sr andMg₂Sr change with elevated temperature, when the temperture is above 423 K, Al₂Sr is more stable than Mg₁₇Al₁₂phase, and Sr addition to the Mg–Al base alloys can improve the creep properties. The calculated bulk modulus (B), anisotropy values (A), Young’s modulus (E), shear modulus (G) and Poisson ratio (ν) showed that Mg₂Sr is ductile, on the contrary, Mg₁₇Al₁₂and Al₂Sr are both brittle, and among the three phases Mg₂Sr is a phase with the best plasticity. The calculations of the density of states (DOS) and Mulliken electronic populations showed that the reason of Al₂Sr having the highest structural stability attributes to Al₂Sr phase having the more covalent bonds compared with Mg₁₇Al₁₂ and Mg₂Sr phases, while Mg₁₇Al₁₂ phase having more stable structure is the result of co–action of ionicand covalent bonds.