Microstructures and mechanical properties of Mg–5Li–4Sn–2Al–1Zn alloy after hot extrusion

Abstract

In this work, Mg–5Li–4Sn–2Al–1Zn deformed magnesium alloy was prepared and the effects of the extrusion process on its microstructure, texture evolution, and mechanical properties were investigated. The microstructures of as-homogeneous and as-extruded alloys were characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results show that the alloy underwent dynamic recrystallization (DRX) after hot extrusion processes. Drastic refinement occurred in grain size, and the weakening of the basal fiber texture was obvious after the Forward-Parallel Channel Extrusion process, and the microstructure was more uniform. As a result, the mechanical properties of the alloy were superior after the Forward-Parallel Channel Extrusion process, and the best combination of strength and plasticity was obtained after the 105° FPE process. YS, UTS, and EL were 187 MPa, 275 MPa, and 15%, respectively. The increase in strength is mainly attributed to grain boundary strengthening and the pinning effect of shattered particles on the migration of dislocations and grain boundaries. The increase in plasticity can be explained by the activation of non-basal slip and the weakening of the basal fiber texture, the fine grains can coordinate the plastic deformation well and improve the plasticity of the alloy to some extent.