Abnormal creep behavior of Mg–12Gd–1MM–0.6Zr (wt.%) alloy at 300℃

Abstract The creep behavior of extrusion-solution treated (T4) Mg–12Gd–1MM–0.6Zr (wt.%) alloys with different grain sizes at 300 °C was evaluated. Results showed that the creep rate curves presented an abnormal decelerated–accelerated–decelerated evolution in the initial stage, which was caused by creep aging. The accelerated creep rate is caused by the transformation from thin β phase into coarse β1 and β phases; and the transformation of the 3D distribution β phase from the initial single variant to network containing three variants is a key reason for the secondary deceleration of creep rate. On the other hand, as the average grain size increased from 44 μm to 90 μm, the steady-state creep rate gradually decreased, but fracture time continuously increased, so coarse grain is beneficial to creep resistance of the present alloy.