Microstructure and mechanical properties of Mg–Zn–(Nd)–Zr alloys with different extrusion processes

Abstract

The effect of Nd addition and the influence of extrusion processes on the microstructure and mechanical properties of Mg–6Zn–0.5Zr (ZK60) and Mg–6Zn–1.5Nd–0.5Zr (ZKNd602) alloys were investigated. Nd element can obviously refine the microstructure of both as-cast and as-extruded Mg–Zn–Nd–Zr alloy. All of the extruded alloys exhibit a bimodal grain structure composed of equiaxed fine recrystallized (DRXed) grains and elongated coarse unDRXed grains. It is necessary to achieve high strength, particularly the yield strength, for ZKNd602 alloy, when it is extruded with a lower extrusion temperature, a suitable extrusion ratio and a relatively lower extrusion ram speed. In this study, the ultimate tensile strength (UTS), yield strength (YS) and elongation (El) of the extruded ZKNd602 alloy were 421 MPa, 402 MPa and 6.7 %, respectively, with extrusion temperature of 290 °C, extrusion ratio of 18:1 and a ram speed of approximate 0.4 mm·s−1. Meanwhile, the extrusion process has obvious effects on the room-temperature properties but weak effects on the high-temperature properties.