First Principles Calculations Of Three Cast Magnesium Alloys And Their Properties

In this paper, based on the experimental Mg-Zn-Gd, Mg-Zn-Sn, AZ91 three kinds of cast magnesium alloy structure using ab initio methods in computer simulation software CASTEP simulation calculations, and the cohesive energy, formation enthalpy and density of states are the following conclusions.1 Observed using SEM and TEM cast and heat treatment of Mg-Zn-Gd(GZ62) alloys and found cast alloy from the Mg matrix and eutectic composition in the grains associated with Mg3Gd phase.6h solid solution alloy at 450℃was found with almost no dissolved Mg3Gd, but were spent by 360℃for 8h and 230℃for 36h found Mg3Gd phase disappears, there has been a long periodic structure organization, with the decress of its mechanical properties. By Mg3Gd phase and long periodic structure(MgZnGd) calculations show that, Mg3Gd than MgZnGd phase stability, and with the experiments.2 There are phases of Mg3Gd in cast Mg-Zn-Gd(GZ62), majority of Mg3Gd vanished after solid solution and heat treating and have long-periodic structure(LPSO) while its mechanical property reduced. By calculation Mg3Gd and LPSO, the stability of Mg3Gd is higher than LPSO. Mg3Gd has invigoration effect on GZ62 alloy.3 AZ91 magnesium alloy were added to 1%and 4%of the Gd element, theβelement was found to increase with Gd, the volume reduction of grain boundary phase, granular A12Gd phase increased to improve its mechanical properties. At the same time Mg3Gd, Mg5Gd and A12Gd stability of three-phase calculation and analysis, the results show that the three-phase stability A12Gd> Mg3Gd> Mg5Gd, alloy forming ability A12Gd> Mg3Gd> Mg5Gd. This shows that the addition of Gd in AZ91 magnesium alloy element of Gd why only A12Gd phase precipitation. This electronegativety judgments consistent with the results, but also verify the Al-RE alloy than to stability.