The amorphous/crystalline (A/C) dual-phase structure is a new design strategy to improve the comprehensive performance of Mg alloys. However, the regulation mechanism of the amorphous phase size of the dual-phase Mg alloys is still unclear. Here, the mechanism and size effect of solid-state amorphization of the dual-phase Mg alloys is investigated using molecular dynamics/Monte Carlo simulations. The results indicate that the degree of solid-state amorphization of the dual-phase Mg alloys depends on three factors: the original size of amorphous phase, the diffusion of rare earth element Y, and A/C interface (ACI). The degree of solid-state amorphization of the alloys exhibits a significant size effect on the original size of amorphous phase. Except for the two models with the smaller original size of the amorphous phase, the degree of solid-state amorphization of the alloys decreases significantly with the increase of the original size of amorphous phase. It is worth noting that after relaxation, as the original size of amorphous phase increases, the distribution of Y atoms in the amorphous phase undergoes a transition from uniform distribution to segregation, and the larger the original size of amorphous phase, the more obvious the segregation phenomenon becomes. The results indicate that the segregation of Y atoms in the amorphous phase suppresses the solid-state amorphization of the alloys. The results show that the segregation of Y atoms in the alloys requires a larger original size of the amorphous phase and the presence of ACI, both of which are essential.
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