Deformation and fracture behavior of Mg alloy, WE43, after various aging heat treatments

Wrought Mg alloy, WE43, is normally artificially aged after hot working (T5 temper). A solutionizing heat treatment is revealed to weaken the initial basal texture of the hot-rolled plate, which resulted in a reduction of the yield strength anisotropy (by notably lowering the in-plane strength). Solutionizing followed by peak aging (T6 temper) only leads to a marginal increase in hardness. The precipitate size and volume fraction are slightly greater for T6 as compared to T5. Different strategies to increase the number density of the precipitates were explored. T8 treatments (where the solutionized material is cold-deformed prior to aging) were carried out, and although the aging kinetics improved, the peak hardness did not. Similarly, two-step aging (first at 140 °C for 4 h, followed by 210 °C) treatment provided no measurable increase in hardness. The T6 samples showed large grain boundary precipitates and a larger precipitate free zone, as compared to T5, which resulted in extensive intergranular ductile fracture, and reduced ductility. Finally, the lower ductility along the plate normal direction is related to stringers of Y-rich cuboidal dispersoids. The results reveal the incumbent T5 temper to be an optimum in terms of strength, ductility, and energy consumption.