Effects of twinning time node on the creep properties of dilute Mg–Y alloy

In this study, the effects of twinning time node on the creep resistance of an extruded Mg-2wt%Y sheet were investigated. Pre-compression with a low strain was applied along the normal direction at 298 K before creep, resulting in a large amounts of {101‾2} twins. For comparing, the samples with and without pre-compression are referred to as PC and NPC, respectively. Compressive creep tests were performed along extrusion direction at 473 K and applied stress ranged from 30 to 70 MPa. The results showed that PC samples present a higher creep resistance than NPC samples. Using various characterization methods, different dominant creep mechanisms were found in two types of samples. The dominant creep mechanisms of NPC sample are cross-slip and twinning while pyramidal slip dominates PC sample. Furthermore, it was verified that cross-slip containing dislocations can easily penetrate into the twins activated during creep, leading to a lower creep resistance. Inversely, the preset twins can slow down the creep rate by retarding cross-slip.