Microstructure and texture evolution during hot rolling and subsequent annealing of Mg–1Gd alloy

Abstract

The microstructure, texture and tensile ductility of Mg–1Gd alloy were investigated and compared to pure Mg following multipass rolling at 300°C and isothermal annealing at 400°C. The addition of Gd weakens the basal texture in both the as-rolled and annealed conditions, which is related to the enhanced activity of pyramidal 〈c+a〉-slip during hot rolling and the suppressed grain boundaries migration due to Gd segregation at grain boundary during annealing. A large number of secondary twins and shear bands formed during hot rolling of Mg–1Gd sheet may serve as favorable nucleation sites for static recrystallization during annealing. The recrystallized grains at bands/twins in Mg–1Gd alloy display a wide spread of orientations, which is similar to that in conventional Mg alloys. Pure Mg sheet shows a strong {0002} 〈11−20〉 texture component due to the preferred growth of grains with the 〈11−20〉 component during annealing. However, Gd solute segregation at grain boundary could inhibit the preferred growth of 〈11−20〉 grains, leading to a weak basal texture and a single 〈10−10〉 texture component in Mg–1Gd alloy sheet after annealing. The room-temperature ductility is significantly improved by the addition of Gd, which is mainly attributed to the texture weakening and grain refinement.