Microstructure and mechanical properties of rolled ZK60 alloy

This solid solution ZK60 magnesium alloy is hot-rolled with different rolling passes and temperatures to fabricate high-property magnesium alloy sheets, and the relationship between the microstructure and mechanical properties of the rolled ZK60 alloy is investigated in detail. The results show that the grain size can be significantly refined from 120 μm in the solid-solution sample to 2.5 μm in the rolled sample. The ratio of recrystallized grains in the fifth pass reaches 89 %, which contributes mainly to the ductility. As the rolling temperature decreases from 400 °C to 350 °C, a small amount of MgZn 2 phase appears. When the rolling temperature further decreases to 200 °C, the number density of second-phase particles reaches 353/μm 2 , approximately 28 nm in diameter. The second-phase particles consist of MgZn 2 phase and rod-shaped Zn 2 Zr 3 phase, which has a size of 15 nm in diameter and 35 nm in length. The rolled ZK60 alloy maintains the combination of high strength and excellent ductility, and the yield strength, ultimate tensile strength, and elongation of the fifth-pass ZK60 alloy is 244 MPa, 300 MPa, and 16 %, respectively. The fine-grain strengthening and precipitation strengthening are the main contributors to high strength, while fine-grain and weak texture mainly contribute to high ductility. Compared with post-extrusion rolling processes, the R5 process reduces production costs significantly, making it suitable for large-scale production.