Comparison of grain size dependence on the creep performance of a Mg-Y alloy along different loading directions

This work precisely investigated the compressive creep behaviors of Mg-4.5 wt%Y alloys with grain sizes ranging from d = 10 mu m to d = 160 mu m. The compressive creep tests were conducted on the hot-rolled sheet at 493 K under 100 MPa with the loading direction along the rolling direction (RD) and normal direction (ND). It was discovered that the compressive creep resistance of the RD sample was decreased with increasing grain size because the grain boundary strengthening and the pyramidal dislocations hardening improved the compressive creep resistance of the samples with fine grains (d = 10 mu m and d = 15 mu m), while {1012} twinning and high-density dislocations decreased the compressive creep resistance of the samples with coarse grains (d = 25 mu m to d = 160 mu m). Differently, cross-slip was inhibited and dislocation climb was promoted with increasing grain size, resulting in the grain size independence of compressive creep resistance in the ND samples. As a result, the compressive creep anisotropy was continuously increased with increasing grain size. It is hoped that this work can provide important reference to the physic modeling of compressive creep behaviors in Mg-RE alloys.