Microstructure evolution and mechanical properties of industrial scale samples of Mg–Gd–Y–Zn–Zr alloy after repetitive upsetting-extrusion process

Abstract

As one of the severe plastic deformation (SPD) methods, repetitive upsetting-extrusion (RUE) technique was an effective way to refine grains for large-sized billet at blank-making stage. The microstructure evolution and mechanical properties of industrial-scale Mg–9Gd–3Y–2Zn–0.4Zr (wt.%) alloys were comprehensively investigated in this paper. The experimental alloys exhibited heterogeneous microstructure in the different regions and directions due to the uneven deformation temperature and strain during the RUE deformation process. In addition, the texture and mechanical properties of the RUEed samples also exhibited obvious anisotropy. In particular, the RUEed sample in the edge region along extrusion direction (EED) showed a superior tensile strength with ultimate tensile strength (UTS) of 357 MPa, tensile yield strength (TYS) of 242 MPa and the failure elongation (FE) of 9.0%, due to the smaller average grain size (12.7 μm) and higher area fraction of the dynamic recrystallized (DRXed) grains (82.2%) than other regions. Furthermore, the results also exhibited that the enhancement of the mechanical properties of the RUEed samples were mainly attributed to Hall–Petch strengthening, Orowan strengthening and texture strengthening.