Effect of cryogenic treatment prior rolling on microstructure and mechanical properties of AZ31 magnesium alloy

Abstract:

The effects of cryogenic treatment prior hot rolling on the strength toughness and ductility of as-cast AZ31 magnesium alloy plate was investigated in this study. The cryogenic treatment conditions were ?60 °C/12 h, ?120 °C/12 h, ?180 °C/12 h, ?60 °C/2 h, and ?180 °C/2 h. Experimental results indicated that appropriate cryogenic treatment conditions can significantly refine the grain size and the strength, toughness and ductility were also improved. A large number of twins appeared in both kinds of samples cryogenically treated for 2 h. The grain size of the sample, which experienced cryogenic treatment for 12 h at ?60 °C followed by rolling process was the finest and most uniform. By increasing cryogenic treatment duration to 12 h, the yield strength of the AZ31 magnesium alloy was enhanced by 25.8% after rolling under ?60 °C cryogenic treatment temperature. Meanwhile, a four-time increase in extension rate (3.06% to 12.31%) was attained. The tensile fracture presented a mixed-mode fracture, which is characteristic of brittle and ductile fracture mechanisms.