Investigation of microstructure and texture evolution in an AZ31/Mg-Gd alloy hybrid metal fabricated by high-pressure torsion.

Abstract

High-pressure torsion (HPT) processing was successfully applied to fabricate a novel hybrid material from separate discs of AZ31 (Mg-3Al-1Zn, wt.%) and Mg-0.6Gd (wt.%) alloys by straining through numbers of rotations, N, of 1/4, 1/2, 5, 10 and 20 turns at room temperature. The microstructure and texture were investigated near the bonding interface through the disc diameter using Electron Backscatter Diffraction (EBSD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The microstructure exhibited two grain refinement regimes with the first occurring during an equivalent strain range, εeq, of ~0.3–72 and the second during εeq from ~72–517. The general texture changed from B-fiber to Y-fiber and C2-fiber through the HPT processing. The resultant microstructures and textures of this hybrid alloy are examined separately for the AZ31 and Mg-0.6Gd alloys and found controlled by the presence of twinning, slip systems and second phases and the occurrence of different dynamic recrystallization mechanisms.