Computation on vacancy diffusion properties of Mg1-xScx alloys in α and β phase
MgSc alloy represents the lightest shape memory alloy identified hitherto and holds broad application prospects in domains,such as the aerospace and the automotive industry. The vacancy formation energy and migration energy in α and β phase Mg1-xScx(x=0.2,0.3,0.5,0.7) alloys were calculated by using a special quasi-random structure combined with first-principles calculation method. The results show that,in the same composition alloy,the change of the number of Sc atoms in the first neighbor of the vacancy has a greater effect on the single vacancy formation energy of α phase MgSc alloy,while the effect on β phase is small. With the increase of Sc content in the alloy,the range of vacancy formation energy increases significantly,indicating that Sc doping makes it more difficult to form vacancies and reduce the vacancy concentration. In different composition MgSc alloys,the Sc vacancy migration energy is greater than the Mg vacancy migration energy,indicating that the diffusion of atoms is mainly completed by Mg atoms,and the vacancy migration energy of Mg atoms in β phase is lower than that of Mg atoms in α phase,which means that after the same aging treatment,the ordered process in MgSc alloy may be more likely to occur in β phase.
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