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采用基于密度泛函理论Castep和Dmol程序软件包,计算了Mg-Al-Ca合金系金属间化合物的力学性质与热力学性能。结果显示:DI3型结构Al4Ca为延性相,C15型结构Al2Ca与C14型结构Mg2Ca为脆性相,C15型结构Al2Ca塑性最差;采用弹性常数计算结果预测的Al2Ca熔点与实验值很接近,误差仅为4.06%;而不同温度下热力学性能的计算结果表明,在298.15~425K温度范围内,Al2Ca的Gibbs自由能最小,对应其相结构的热稳定性最好;而Al4Ca次之,Mg2Ca最差;随着温度的升高,Mg2Ca的Gibbs自由能下降最快,对应结构的热稳定性增强也最快;在525K以上时,Mg2Ca的结构热稳定性最好,其次是Al2Ca,而Al4Ca最差。
The mechanical properties and thermodynamic properties of the Mg-Al-Ca alloy intermetallic compounds have been calculated using the software package of Castep and Dmol based on density functional theory. The results show that Al4Ca of DI3 structure is ductile phase, Al2Ca structure of C15 structure and Mg2Ca structure of C14 structure are brittle and Al2Ca structure of C15 structure is the worst. The calculated melting point of Al2Ca is close to the experimental one 4.06%. The calculated results of thermodynamic properties at different temperatures show that the Gibbs free energy of Al2Ca is the lowest in the temperature range of 298.15 ~ 425K, the thermal stability of Al2Ca is the best, followed by Al4Ca and Mg2Ca are the worst. With the increase of temperature, the Gibbs free energy of Mg2Ca decreases fastest, and the thermal stability of the corresponding structure increases fastest. When the temperature is above 525K, the structure thermal stability of Mg2Ca is the best, followed by Al2Ca and Al4Ca is the worst.