Enhancing mechanical properties of AZ61 magnesium alloy via friction stir processing: Effect of processing parameters

The purpose of this study was to modify the microstructure and mechanical properties of AZ61 cast magnesium alloy via solid-state friction stir processing (FSP). The effect of processing parameters on the microstructural evolution, texture and mechanical behavior was investigated. The results indicate that FSP was capable of producing fine-grained AZ61 magnesium alloy through dynamic recrystallization, and eliminating the unfavorable network-like large β-Mg17Al12 particles present along the grain boundaries in the cast magnesium alloy. With increasing ratio of rotation rate to traverse speed, the grain size and fraction of high-angle grain boundaries (HAGBs) increased. Compared with the original cast alloy, the microhardness and tensile properties of FSP specimens were significantly enhanced. The high strength and ductility of FSP specimens were achieved mainly due to the scattered distribution of crystallographic texture and the effective grain refinement along with a larger fraction of HAGBs.