Synergistic effects of grain refinement and texture weakening on mechanical properties anisotropy of Mg-9Gd-4Y-2Zn-0.4Zr alloy via RUE processing

Abstract

The effect of repetitive upsetting and extruding (RUE) on microstructure, texture and mechanical properties anisotropy of Mg-9Gd-4Y–2Zn-0.4Zr alloy was investigated. The influences of the RUE on the microstructural characteristics and microhardness of different direction were explored. The microstructures were observed by using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD). Results showed that grain refinement and texture weakening had a positive role in mechanical anisotropy with the increase of RUE passes, the alloy exhibited smaller size difference of each direction. At the same time, the difference of Schmid factors for basal slip was greatly reduced accordingly. The grain size difference of each direction was mainly caused by the difference of long-period stacking ordered (LPSO) phase evolution and dynamic recrystallization (DRX) fraction. The microhardness difference of each direction was reduced with the RUE process. Under the dual stresses of upsetting and extrusion, the spread of the basal pole and the rotation of the main texture caused the activation of non-basal slip. RUE process allowed plastic deformation to continue, resulted in grain refinement and reduced anisotropy. Texture weakening and grain refinement played a synergistic role in weakening the mechanical properties anisotropy.