Static recrystallization behavior of multi-directional impact forged Mg-Gd-Y-Zr alloy

The static recrystallization behavior of a (Mg-9.02Gd-4.21Y-0.48Zr wt.%) GW94 alloy during annealing treatment in the temperature range of 350–500 °C has been investigated by means of electron backscattered diffraction (EBSD). To investigate the role of twin boundaries in static recrystallization of GW94 alloy, a large number of {10–12} extension twins were introduced initially by multi-directional impact forging (MDIF) process. After the MDIF process, coarse grains containing parallel and intersected twins while small grains containing only parallel twins were observed. It has been observed that twin/grain boundaries (TBs/GBs) are stable at 350 °C, but static recrystallization governed by the increased twin/grain boundary mobilities begins at the 400–450 °C temperature range. Microstructure evolution during static annealing reveals that nearly all pre-existing {10–12} extension twins start to recrystallize at 400 °C and 60 min, yet few parallel twins plus residual twin traces with misorientations of 5°–10° were observed. In contrast to the parallel twins in both large and small grains, the intersected {10–12} extension twins in coarse grains were found to be unstable and more effective to induce recrystallization.