Microstructure and mechanical properties of AZ61 Mg alloy during isothermal multi-axial forging （MAF） were studied. The mechanisms of grain refinement and relationship between the microstructures and mechanical properties were discussed. The results show that the average grain size decreases with increasing the number of MAF passes. The grains are significantly refined at the 1st and 2nd MAF passes, and gradually refined at higher MAF passes. The initial grain size of 148 lam decreases to about 14 gm after 6 MAF passes. The grain refinement occurs mainly by continuous dynamic recrystallization. With increasing the MAF passes, both the tensile strength and the elongation to failure of the alloy are significantly enhanced.
