Strain induced GdH2 precipitate in Mg–Gd based alloys

A new rectangle-shape GdH2 precipitate was identified in Mg–Gd based alloys after mechanical polishing or compressive deformation. The precipitate was mainly distributed near the dendrite or grain boundaries where gadolinium element was segregated owing to non-equilibrium solidification. It is confirmed that hydrogen-containing medium, deformation and gadolinium segregation were the prerequisites to form GdH2 precipitate. The amount of GdH2 precipitate was mostly associated with deformation and the gadolinium content. A model was introduced to explain the formation mechanism of GdH2 precipitate. The hydrogen in GdH2 precipitate principally came from the outside medium. Moreover, the diffusion and transportation of hydrogen were improved by the movement of dislocation.