Mg13Al14和Mg17Al12中间合金的第一性原理研究

First-principles Study of Intermediate Alloy Mg13Al14 and Mg17Al12

Mg-Al合金具有密度小、刚度好、强度质量比极佳、可铸性以及延展性良好等优点,可作为一种性能优异的轻量级结构材料。Mg17Al12作为其中的中间合金,具有阻碍位错运动来强化晶界的重要作用。本工作采用第一性原理方法,系统研究了Mg13Al14和Mg17Al12两种中间合金的晶体结构、电子结构及力学性能。研究结果表明:Mg13Al14的原胞结构不具有热力学稳定性,而Mg13Al14初胞结构热力学稳定,且稳定性高于Mg17Al12;通过电子结构分析发现,Mg13Al14和Mg17Al12均具有很强的金属性,且Mg17Al12的离子性略强于Mg13Al14,因此Mg17Al12具有更高的结构稳定性;通过力学参数计算,可以得出二者的初胞均具有良好的力学稳定性,而Mg13Al14的原胞不具有力学稳定性。其中Mg13Al14表现为延性材料,Mg17Al12表现为脆性材料;Mg13Al14初胞的可塑性更好,抵抗剪切形变的能力强于Mg17Al12;Mg17Al12的刚性更高,抗塑性变形能力强于Mg13Al14;Mg13Al14和Mg17Al12均表现为弹性各向异性;对于Mg-Al合金,中间合金初胞结构的Mg13Al14的综合力学性能优于Mg17Al12,但原胞的热力学稳定性较差,与Mg17Al12相比不利于提升Mg-Al的热稳定性。

In this paper,the crystal structure,electronic structure and mechanical properties of intermediate alloy Mg 13 Al 14 and Mg 17 Al 12 were studied by first-principles method. The results show that the primitive cell structure of Mg 13 Al 14 has no thermodynamic stability,but its conventional cell structure is thermodynamically stable and its stability is higher than that of Mg 17 Al 12;Mg 13 Al 14 and Mg 17 Al 12 both have strong metallic properties,Mg 17 Al 12 has higher structural stability,Mg 13 Al 14 has no mechanical stability;Mg 13 Al 14 is ductile material,and Mg 17 Al 12 is brittle material. In addition,the ability to resist shear deformation of Mg 13 Al 14 ’s conventional cell structure is stronger than Mg 17 Al 12;Mg 17 Al 12 has higher rigidity and stronger resistance to plastic deformation than Mg 13 Al 14;both Mg 13 Al 14 and Mg 17 Al 12 exhibit elastic anisotropy. It is suggested that the general mechanical properties of Mg 13 Al 14 ’s conventional structure are better than that of Mg 17 Al 12 ,but the thermodynamics of the primitive cell is unstable. Consequently,comparing with Mg 17 Al 12 ,Mg 13 Al 14 is not conducive to improving the thermal stability of Mg-Al alloy.