Optimization of Rolling Condition for ZK61 Alloy Sheets via Microstructure and Mechanical Property Analysis

To explore the proper rolling parameters for industrial sheet fabrication, hot-extruded ZK61 magnesium alloy sheets with 2 mm thickness were fabricated by multi-pass hot rolling at gradually decreasing temperature with 20, 30 and 40% thickness reduction ratios. As the rolling proceeded, the extent of grain size refinement as well as microstructure uniformity was improved continuously via multiple dynamic recrystallization. The rolling deformation resulted in the formation of a strong (0002) basal texture accompanied by the increasing of (0002) pole intensity along TD but the decreasing of that along RD. Tensile tests at room temperature revealed that the enhancements of mechanical properties and its isotropy in RD–TD plane were attributed to both grain refinement and texture variation. The relations between microstructure and mechanical properties were discussed in detail on the basis of experiment in this article. Weighted by the microstructure and mechanical properties, the optimum rolling process was determined as the multi-pass hot rolling with 30% thickness reduction ratio for as-extruded ZK61. Under this condition, a uniform structure with a grain size of about 7.3 μm was obtained, and a comprehensive mechanical performance was achieved with yield strength of 194.1 MPa, ultimate tensile strength of 301.3 MPa and total elongation of 23%.