Unusual microstructure and texture transition during hot compression in an extruded Mg-Gd-Zr alloy with <0001> fiber texture

In magnesium (Mg) alloys with high rare earth content, slip modes and twinning behaviors are quite different from that in traditional Mg alloys. Deformation mechanisms, i.e., {11−21} twinning and non-basal slips, can activate during deformation process even at room temperature (RT) and contribute effectively to microstructure and texture transition. In order to figure out the influence of temperature on these deformation mechanisms and resultant microstructure and texture transition, compression tests were conducted on an extruded Mg-17.5Gd-Zr (wt%) alloy with <0001> fiber texture at temperature range of RT-450 °C. During compression, both {10−12} and {11−21} twinning behaviors can be governed by Schmid law at RT-350 °C and act as main contributors to texture transition. When the compression tests were carried out above 400 °C, twinning behaviors almost vanished and dynamic recrystallization (DRX) preferred activating within grains with the orientation of <10–10>//compression direction. DRX changed from continuous DRX to discontinuous DRX with the temperature increasing, which can be attributed to the temperature increasing and resultant elimination of sessile structure induced by cross-slip on basal plane. DRXed grains show weak texture and the texture mainly result from the properties of several near coincident site lattice boundaries.