Investigation of the optimum preheating treatment parameters for extruded Mg–Gd–Y–Zn–Zr alloy using high-throughput experiments

Abstract

The effects of different preheating treatments on the microstructure and mechanical properties of extruded Mg–13Gd–4Y–2Zn–0.5Zr (wt.%) alloys were investigated by using high-throughput experiments in this paper. The results showed that the solid solution and aging prior to extrusion (SAE) samples with heterogeneous microstructure had the best strength-plasticity synergy with ultimate tensile strength (UTS), yield strength (TYS) and elongation (EL) reaching 446.35 ± 3.1 MPa, 382.5 ± 2.5 MPa and 6.5 ± 0.8%, respectively. The formation of heterogeneous microstructures was mainly attributed to the weakening of the particle stimulation nucleation (PSN) effect by the dissolution of the primary Mg5RE phase during the solid solution process and the strong Zener pinning effect of the dynamic Mg5RE phase precipitation during the extrusion process, which inhibited grain boundary migration and grain growth. Optimum strength-plasticity synergy was due to fine grain strengthening, second phase strengthening, texture strengthening and heterogeneous deformation induced (HDI) strengthening. Strain gradients between deformed grains and dynamic recrystallized (DRXed) grains were generated during deformation process, in order to coordinate the deformation and generate more geometrically necessary dislocations (GNDs) within the deformed grains, resulting in a strong HDI effect. The increase in plasticity was mainly attributed to the change in texture type due to the rotation of the lattice, which promoted the activation of non-basal slip systems. This study provided an efficient and rapid method for probing optimal heat treatment parameters, aiming to reduce the influence of uncontrollable factors on experimental results and increase the rigor of the experiment.