Tensile creep anisotropy and its weakening mechanism in a dilute Mg-Ca alloy

The tensile creep anisotropy of a dilute-alloyed Mg-0.3wt%Ca sheet is investigated along the rolling direction (RD) and normal direction (ND). Strong creep anisotropy is shown between the RD and ND, owing to the easy twinning and the Ca-segregation along twin boundaries during creep loading along the ND. To weaken the creep anisotropy, hot-compression parallel to the RD-ND plane is performed and the continuous dynamic recrystallization mechanism induces a bimodal microstructure with the coexistence of unrecrystallized and recrystallized grains. The creep anisotropy is successfully weakened after hot-compression, and the creep resistance is also significantly enhanced along both loading directions. With the assistance of microstructural characterization, the weakened creep anisotropy is ascribed to the dislocation arrays in the interiors of recrystallized grains and the Ca-segregation along the boundaries of recrystallized grains. Compared to commercial Mg alloys with poor creep property and rare-earth alloyed Mg with high price, good creep performance and low production cost can be synchronously realized in the hot-compressed Mg-0.3wt%Ca alloy. Thus, this work proposes a new perspective for producing creep-resistant Mg alloys.