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Has a low density, stiffness and high specific strength, electromagnetic shielding ability, magnesium alloy and magnesium alloy easily recovered excellent performance is a good lightweight structural materials, has been widely used in the aerospace, electronics, and automobile industry. However, due to the magnesium alloy itself stretching limited strength, ductility, flammable and high-temperature creep resistance, so that in the field of modern industrial economy practical application of magnesium alloy market is still very limited. In order to further improve the mechanical properties of magnesium alloy, a large number of experiments to explore, experimental studies have shown that adding rare earth elements can significantly enhance the mechanical properties of magnesium alloy. However, most of the work on the magnesium alloy is limited to the experimental study is still relatively small in terms of theoretical research, especially the lack of study of the mechanism of plastic deformation of magnesium alloy. In recent years, based on the generalized plane layer fault energy to study deformation mechanism of the alloy of the face-centered cubic structure has aroused widespread concern. In this paper, using first-principles calculation method based on the density functional theory (DFT) to study the Al-Mg-Sc alloy phase deformation mechanism and mechanical properties, In addition, on the rare earth elements and some mechanical properties of pure magnesium surface and base of the wrong The influence of the study and discussion. The main contents are as follows: 1. Using first-principles calculation of the binary face-centered cubic structure in Al-Mg-Sc alloy phase Al 3 Sc and Al 3 Mg generalized plane layer fault energy curve, and stacking faults of the three-layer thickness is the smallest twin nuclei, which is consistent with Mahajan et al reported. And Al 3 Sc and Al 3 Mg twinning of the ability to carry out a comparative study. The calculated Al 3 Sc and Al 3 Mg in the surface energy, and According to Rice criterion, respectively, to determine if they ductility strength. The calculated density of states and the charge density is further revealed from the microscopic deformation mechanism of the slipping process, results show that: the hybrid orbital effect dramatic changes and the valence electron charge density at the stacking fault exists, and thus led to the Al 3 Sc and Al , 3 Mg has a high stacking fault energy, and therefore more difficult to dislocation nucleation occurs. 2 through the calculation of the density functional theory, were obtained adding Y, Sc, Nd, Eu and Er, the magnesium alloy after most easily slip plane generalized stacking fault energy curve, the results show that: These rare earth elements to significantly reduce the stacking fault energy of pure magnesium, especially unstable stacking fault energy, which makes the epitaxial-type partial dislocation occurs trend becomes stronger, but also make the the ductility transition of magnesium alloy better. Rice criterion shows that Eu was added, and the ductility of magnesium alloy.
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