Effect of partial rolling and heat treatment on the microstructure and mechanical properties of AZ80 Mg joint

AZ80 Mg alloy joints were submitted to solution treatment, partial rolling processes at 300 °C, 350 °C and 400 °C, and subsequently aging treatment at 180 °C. As the rolling temperature increased, recrystallization ratio increased and strain hardening effect was weakened which could reduce the crack tendency in the weld. Rolling at around 350 °C, strain hardening and fine grain strengthening obtained a good combination; the porosity in the weld can be effectively eliminated, resulting in significant improvement of tensile properties. The precipitation behavior of Mg17Al12 phase was different in various areas of the partially rolled joints. Spherical Mg17Al12 phase preferred to precipitate in the as-deform microstructure, in particular inside the twins. While continuous Mg17Al12 phase and cellular discontinuous Mg17Al12 phase would not form inside the twins due to the unfavorable orientation. The pinning effect of Mg17Al12 precipitates led to further strengthening for the joints during the aging treatment.