Preparing strong and ductile AZ80 Mg alloy via warm rotary swaging

Rotary swaging at different temperatures has been conducted to process the AZ80 Mg alloy rods, and the results are compared. Rotary swaging to an equivalent strain of 0.25 at room temperature, induced high densities of deformation twins and macrocracks, causing catastrophic failure of the swaged rods. In contrast, repetitive conduct of 260°C-swaging and water cooling promotes <c + a> dislocation slip and localized grain refinement via twinning and dynamic recrystallization, and thus to lower the number of large twin bands in coarse grains. The sample processed by 260°C-swaging and water cooling has a nano-structural hierarchy consisting of bimodal grain size distributions and high densities of nano-precipitates located at grain boundaries of the ultrafine grains and at coarse-grain interiors, and shows a gradient hardness distribution from the periphery to center of the rod; Correspondingly, the 260°C swaged sample shows outstanding combinations of strength and ductility at both the peripheral and central regions.