On the microstructure and RE-texture evolution during hot tensile deformation of Mg-Gd-Y-Zn-Zr alloy

Abstract

This study was conducted to investigate the correlation between the microstructure/texture evolutions and the high temperature flow behavior of Mg-8.3Gd-3.6Y-1.6Zn-0.5Zr (wt. %) alloy containing long period stacking order (LPSO) phases. Toward this end, the hot tensile tests were conducted at 350 and 400 °C on two different starting microstructures: (i) as-extruded containing blocky LPSO, and (ii) as-annealed, which contained both blocky and lamellar LPSO phases. The peak stresses of the annealed microstructures at 350 and 400 °C, i.e. 200 and 80 MPa, were almost twice that of extruded ones at the same temperatures, i.e. 117 and 39 MPa, respectively. The annealing treatment effectively strengthened the alloy and decreased the ductility value. This was justified relying on the grain growth, deformation twinning and texture evolution, but a special emphasize was paid on the effect of lamellar and blocky LPSO phases. It was found that the blocky LPSO could assist the dynamic recrystallization through activation of particle stimulated nucleation (PSN) mechanism and effectively contributed in the formation of rare earth (RE)-texture component. This provided high Schmid factors for operation of basal slip and improved the ductility values. On the contrary, the fine lamellar LPSO effectively increased the strength of the alloy via texture hardening but reduced the ductility. The lamellar LPSO played a key role in the formation and strengthening of the <10-10> fiber texture, retarded the recrystallization process and suppressed the formation of RE-texture component.