Effects of reduced extrusion temperature on microstructure and mechanical properties of Mg–6Zn–0.5Zr alloy
Shuhui Lv, Qiang Yang, Xiaoling Lv, Fanzhi Meng, Xin Qiu
Abstract
Improving the strength of the commercial ZK60 alloys plays a key role in promoting their wide applications. In this work, a ZK60 alloy was prepared by conventional direct extrusion at an obviously reduced temperature of 180 °C. Compared with ZK60 alloys directly extruded at high temperatures (>300 °C), the studied alloy has finer dynamic recrystallized (DRXed) grains with the average size of ∼1.7 μm, stronger typical fiber texture and more profuse lath-like sub-grains. In addition, the ultra-low extrusion temperature increased dynamic precipitates (rod-like Mg4Zn7 and MgZn2) in DRXed grains. After aging, a great many of nanosized precipitates formed in both DRXed grains and non-recrystallized grains, and relatively coarse MgZn2 particles precipitated on sub-grain boundaries. As a result, the aged ZK60 alloy exhibit significantly high ultimate compressive strength of ∼675 MPa on the basis of high yield strength of ∼310 MPa, indicating a significant strain hardening capability. Meanwhile, it has excellent strength-ductility balance and a weakened tension-compression yield strength asymmetry under owning a high TYS in order of ∼400 MPa.