Deformation and fracture mechanisms of an annealing-tailored bimodal grain-structured Mg alloy

Through investigating and comparing the mechanical behavior of an as-rolled Mg-3%Al-1%Zn(wt%) alloy before and after annealing treatments, it was revealed that the formation of annealing-tailored bimodal grain structure ensured the 330 degrees C/4 h samples having a good combination of tensile strength and plasticity. Failure analysis demonstrated that for the as-rolled and 330 degrees C/1 h samples with fine grain structure, their plastic deformation was mainly attributed to basal slips, whereas the deformation mechanism in the bimodal grain-structured samples was dominated by basal slips in fine grains and twinning in coarse grains. For the 330 degrees C/8 h samples with coarse grain structure, high densities of twins were activated. Meanwhile, basal slips occurred in the twinned and un-twinned areas of coarse grains and could pass through twin boundaries. For differently treated samples, cracking preferentially occurred along slip bands, resulting in their transgranular fractures. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.