Using ring samples to evaluate the processing characteristics in high-pressure torsion

An Al-3%, Mg-0.2% Sc alloy was processed by high-pressure torsion (HPT) using samples in the form of solid disks and rings. Following HPT, all values of the measured Vickers microhardness fall onto a single curve when plotted against the equivalent strain, such that there are increasing values of hardness at the lower strains and hardness saturation above equivalent strains of similar to 40. This saturation level is independent of the number of revolutions and the applied pressure. The grain size following HPT is similar to 220 nm, and tensile tests show that the material is superplastic at a testing temperature of 573 K. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.