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.
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