Proposed mechanism of twin formation during hexagonal-close-packed structure to face-centered-cubic phase transition

Detailed process, critical energy, and critical shear stress of twin formation during hexagonal-close-packed (HCP) to face-centered-cubic (FCC) transition are proposed through first principles calculation. It reveals that a lower critical energy is needed for HCP→FCC basal transition with twin formation than that without twin. The relative magnitude of critical shear stresses is strongly correlated with c/a ratio of HCP metals, and fundamentally determines the appearance of HCP→FCC basal transition and phase-transition twin. The predicted results bring about reasonable explanations to two puzzling points regarding Mg and twin formation in the literature.