Evolution of microstructure and mechanical properties of AZ61 Mg alloy during cyclic closed die forging

Microstructure and mechanical properties of an AZ61 Mg alloy during cyclic closed die forging (CCDF) were studied. The mechanisms of grain refinement are discussed. The results show that the average grain size decreased with increasing number of CCDF passes; After 6 CCDF passes, the initial grain size of 152 mu m decreased to about 16.5 mu m, and the billet had a uniform microstructure. The grain refinement occurs mainly by continuous dynamic recrystallisation. With increasing numbers of CCDF passes, both the tensile strength and the elongation to failure of the alloy are significantly enhanced.