An Evaluation of Homogeneity and Heterogeneity in Metals Processed by High-Pressure Torsion

Processing through the use of high-pressure torsion is attracting much attention at the present time because of the potential for achieving exceptional grain refinement. In principle, it appears that the thin disks used for high-pressure torsion processing should exhibit significant heterogeneity in the as-processed condition. However, experiments show that the development of homogeneity or heterogeneity is dependent upon the crystalline structure of the material. For high-purity aluminum the as-processed microstructure is very homogeneous after five or more revolutions of torsional straining but for the magnesium AZ31 alloy there is a considerable degree of heterogeneity in the as-processed disks.