Microstructures and tensile properties of Mg-Zn-(Gd)-Zr alloys extruded at various temperatures

The microstructures and tensile properties of Mg-6.0Zn-0.6Zr (ZK60) and ZK60 + 1.8Gd (ZEK620 (RE = Gd)) alloys extruded at 290, 305, 320, 340 and 360 A degrees C were investigated. The results indicate that Gd addition can refine the microstructures of ZK60 alloy and the extrusion parameters such as the extrusion temperature will influence the tensile properties of both as-extruded ZK60 and ZEK620 alloys, although it is much slighter for ZK60 alloy. And the sensitivity is closely related to the textures developed during extrusion. In addition, Gd addition will also clearly improve the tensile strength at room temperature (24 A degrees C) and particularly at high temperatures (150 and 200 A degrees C), due to the much finer grains and smaller intermetallic particles. The highest strength is achieved in the as-extruded ZEK620 alloy with extrusion temperature of 320 A degrees C, with ultimate tensile strength (UTS) and tensile yield strength (TYS) of 405 and 375 MPa, respectively, which are improved by approximately 9% and 11% than those of the as-extruded ZK60 alloy which owns the highest strength at extrusion temperature of 290 A degrees C.