Microstructure and Mechanical Properties of Magnesium Alloy Prepared by Repetitive Upsetting

Repetitive upsetting (RU) was applied to a commercial AZ31 Mg alloy. The samples were processed at temperatures of 230 degrees C, 250 degrees C and 300 degrees C up to 3 passes. Effects of processing temperature on the microstructure and mechanical properties were investigated. The results indicate that the microstructure was effectively refined by RU and an average grain size of similar to 1.9 mu m was obtained at 250 degrees C. Increasing the temperature resulted in larger mean grain size and higher microstructural homogeneity. Both the strength and hardness were significantly improved. It was also found that increasing the processing temperature led to increase in the strength but decrease in the ductility. The sample after RU 3 passes at 230 degrees C had tensile strength of 330 MPa compared with 173 MPa prior to the processing.