Annealing Effects after Various Thermo-Mechanical Treatments on Microstructure and Mechanical Properties of Wrought Magnesium Alloy ZK60

The magnesium alloy ZK60 received from Dead Sea Magnesium in direct-chill cast condition was extruded at T = 350C using an extrusion ratio of ER = 12. The extruded bars were severely plastically deformed at 250C by either equal channel angular pressing or swaging. While swaging led to similar grain refinements as observed after equal channel angular pressing, yield stress and tensile strength values were by far superior in the swaged material. This result is explained by the unfavourable 45° texture component of the (0002) pole figure that develops during the massive shear deformation in equal channel angular pressing. Unlike equal channel angular pressing, the grain orientation after swaging is similar as in the as-extruded condition. Annealing at elevated temperatures indicates very low thermal stability of microstructure and mechanical properties in the equal channel angular pressing material while both properties in the swaged microstructure are as stable as in the as-extruded reference.