Anisotropy in the tensile creep behaviors of a hot-rolled Mg-5.5wt%Y alloy sheet

In this work, the tensile creep anisotropy was investigated in a hot-rolled Mg-5.5 wt%Y alloy sheet. The loading directions were performed along rolling, transverse and normal directions (RD, TD and ND), respectively. The results showed that a poor creep resistance was obtained along ND due to serious stress concentration induced by high-density twin boundaries blocking dislocations. While a similarly excellent creep resistance was obtained along RD and TD due to pyramidal slip contributes to the strain hardening during creep process. Meanwhile, this work found that an addition of 5.5 wt%Y could enhance the crack resistance of grain boundary over that of twin boundary. When twin boundaries were heavily generated to block dislocations during tensile creep, crack initiation occurred rapidly. It is suggested that both the density of twin boundaries and the Y content should be considered for improving the creep resistance of Mg Y based alloys.