Influence of strain rate on the characteristics of a magnesium alloy processed by high-pressure torsion

A commercial magnesium AZ31 alloy was processed by high-pressure torsion (HPT) through 5 turns at 453 K using three different rotation rates. The results show that HPT introduces significant grain refinement to an average grain size of ∼0.5 μm. The processed structures were heterogeneous in the centers of the disks and homogeneous at distances at and above ∼1 mm from the disk centers. The measured values of the microhardness were also reasonably homogeneous after HPT except only near the disk centers. The hardness values and the average grain sizes were correlated with the local strain rates by using the imposed rotation rates and estimates of the strains within the disks. The results demonstrate the hardness and the average grain size both exhibit a small dependence on the local strain rate.