Optimization of rolling temperature for ZK61 alloy sheets via microstructure uniformity analysis

Hot rolling of ZK61 Mg alloy sheets with homogeneous structure was performed at the temperature range of 553–433 K to examine the influence of rolling temperature on the microstructure refinement and uniformity. As the rolling temperature decreased, the microstructure was refined continuously with the decrease of Zener–Hollomon parameter via dynamic recrystallization. Detailed investigation of the microstructures revealed that dynamic recrystallization was completed at the temperature above 503 K, and partially from 493 K to 453 K, but did not occur below 443 K. Weighted by their uniformity, the temperature range of 523–493 K can be considered to be the optimum temperature values for hot rolling. Under this condition a uniform structure with a grain size of about 3.0 μm was obtained, and a comprehensive mechanical performance was achieved with tensile strength of 330 MPa, yield strength of 240 MPa and elongation of 24%. In addition, the relations between microstructure and mechanical properties were also analyzed.