Investigation of shear and tensile mechanical properties of ZK60 Mg alloy sheet processed by rolling and sheet extrusion

The microstructure, texture and mechanical behavior of two wrought ZK60 magnesium alloys were investigated by tensile test and shear punch test (SPT). The samples processed by hot rolling and the combination of hot rolling and sheet extrusion techniques. The mechanical properties of the alloys correlated to the microstructural characteristics and the texture. Microstructural analysis showed that extrusion transformed the equiaxed coarse grain structure of the rolled sample with an average grain size of 68 μm to a bimodal structure including very fine dynamically recrystallized (DRX) grains, having an average grain size of ∼2.8, and large elongated deformed grains. The sheet extrusion process improved the tensile yield stress, the ultimate tensile strength, the shear strength, and the tensile elongation to failure. The strength enhancement was attributed to the finer grain size and the change of the volume fraction of the secondary phase particles. It was demonstrated that extrusion could improve both strength and ductility at room temperature in wrought ZK60 alloy. Although the tensile ductility improved after extrusion, it was shown that deformability in SPT remains unchanged after extrusion. Microstructural observations show that in SPT the positive effect of the grain refinement on the ductility was compensated by the hindering effect of Mg4Zn7 particles on the glide of pyramidal dislocations. This slip is a dominant mechanism of deformation during SPT due to the basal texture.