Effect of extrusion conditions on microstructure, texture, and yield asymmetry in Mg–6Y–7Gd–0.5 wt%Zr alloy

A Mg–6Y–7Gd–0.5 wt%Zr alloy has been extruded at a range of temperatures and two extrusion ratios. The grain structure developed after extrusion is controlled by the fraction and distribution of second phase β particle stringers. Extrusion at temperatures below the β solvus leads to bimodal grain structures, with fine grained regions associated with the particles as a result of particle pinning. These grain structures are unstable when they are unpinned during solution treatment. The textures of all extrusions are weak and the dominant component changes with extrusion condition. In particular, extrusions produced with the highest extrusion ratio show an unusual texture component in which the c-axis is aligned parallel to the extrusion direction. This strengthens further on solution treatment. All extrusions show almost no yield asymmetry in axial tension and compression. Modelling suggests this remarkable lack of asymmetry cannot be wholly attributed to texture, but also requires a change in relative critical resolved shear stress (CRSS) for the deformation.