First-Principles Investigations on Structural Stability, Elastic Properties and Electronic Structure of Mg32(Al,Zn)49 Phase and MgZn2 Phase

Al–Mg–Zn alloys reinforced by T–Mg32(Al,Zn)49 phase had higher structure stability and strength than Al–Zn–Mg–(Cu) alloys reinforced by MgZn2 phase, but the reasons for these two kind of alloys was not well-known. To reveal the discrepancy between T phase and MgZn2 phase, the lattice parameters, cohesive energy, and electronic structure as well as the elastic properties were investigated based on density functional theory. Four types of T phase unit cell were employed according to symmetry of space group. The calculated lattice constants well-agreed with experimental data. Compared to MgZn2 phase, T phases obtained lower cohesive energy owing to their partial covalent bond, which may result in a higher structure stability. The elastic modulus E of T phase depended on the occupation of Al atom, and the effect of the occupation of Al atom on the structure and properties of T phase was also discussed.