Achieving homogeneity in a Cu-Zr alloy processed by high-pressure torsion

A copper alloy, Cu-0.1 %Zr, was subjected to severe plastic deformation at room temperature using quasi-constrained high-pressure torsion. Disks were strained through different numbers of revolutions up to a maximum of ten turns under an applied pressure of 6.0 GPa and then examined to evaluate the evolution in the Vickers microhardness, Hv, and the microstructure. The results show lower values of Hv in the center regions of the disks in the early stages of processing but a gradual evolution to a high degree of hardness homogeneity after five and ten turns. Under conditions of hardness homogeneity, the distributions of the grain boundary misorientations are essentially identical at the center and the periphery of the sample. Homogeneity was further confirmed by conducting tensile testing at elevated temperatures where similar stress-strain curves and similar elongations to failure were recorded after processing through five and ten turns of HPT.