Microstructure, crystallographic texture and mechanical properties of the magnesium alloy AZ31B after different routes of thermo-mechanical processing

In this study the hexagonal close packed magnesium alloy AZ31 is deformed plastically by equal-channel angular pressing (ECAP) at 523 K, bi-directional rolling (BR) at 573 K, and by combinations of these processes. The evolution of microstructures, crystallographic textures and of the mechanical properties is investigated systematically as a function of the processing method, the amount of accumulated strain or the ECAP processing route (strain path). Both BR and ECAP enforce a crystallographic reorientation, with an alignment of (0002) basal planes parallel to the direction of shear deformation. This results in significant changes of the strongly texture-dependent mechanical properties. In combined processing, ECAP is applied as a method to increase texture-induced softening and ductility, whereas BR followed by water quenching is used as a method to induce strengthening by work hardening. The aim of tailoring materials and microstructures that are strong, but still ductile, and that can consume a moderate amount of plastic work during deformation, is best met by a combination of ECAP and subsequent BR. The corresponding yield strength of 345 MPa and elongation to failure of 13.9% demonstrate the considerable potential of the novel processing routes presented here for the first time.