Enhanced mechanical properties of a hot-extruded AZ80 Mg alloy rod by pre-treatments and post-hot compression

Abstract

A hot-extruded AZ80 Mg alloy rod was subjected to pre-treatments and post-hot compression in this work. Microstructure evolutions and resultant mechanical properties were investigated using samples with different states. The sample processed by solid solution and pre-aging (SSA) contained large-scale precipitates at the triple points of grain boundaries, while the sample processed by solid solution, pre-deformation and pre-aging (SSPDA) contained fine precipitates and different types of dislocations in the {10–12} twin interiors. Meanwhile, substructures were formed through dislocations surrounding the fine precipitates in SSPDA sample. During hot compression at 593 K, continuous dynamic recrystallization (DRX) was promoted by substructures in SSPDA sample, resulting in a full development of fine grains and a weakened texture. Inversely, discontinuous DRX happened in SSA sample, resulting in a low volume fraction of DRX grains and a relatively strong texture. The tensile testing showed that SSPDA sample had much higher strength and ductility than those of SSA sample. The enhanced mechanical properties were attributed to the completely developed DRX with grain refinement and texture weakening.