Hardening mechanisms contribution at nonmonotonic change of properties in the Cu–0.6Cr–0.1Zr alloy at high pressure torsion

Abstract

Phase transformations play an important role in the formation of properties in the dispersion-hardened alloys, for example, such as the Cu–Cr–Zr system alloys. It is known that under severe plastic deformation, the diffusion conditions change significantly, which leads to a change in the phase transformation kinetics. In this work, the authors studied the Cu–0.6Cr–0.1Zr alloy in the low concentration solid solution state subjected to high pressure torsion (up to 10 cycles). In this case, due to the solid solution low concentration and the formed ensemble of large particles, the process of solid solution decomposition was excluded at the first stages. The preliminary work on the analysis of such structurally sensitive characteristics as electrical conductivity and lattice parameter made it possible to identify the nonmonotonic nature of a change in the alloying elements concentration in the solid solution during HPT. Nonmonotonicity is related to the significant changes in the characteristics of the second phase particles ensemble under the influence of high voltages. Such significant structural changes are reflected in the nature of the mechanical characteristics change. The authors identified that when increasing the number of HPT revolutions, changes in strength also have a nonmonotonic nature, which corresponds to the nonmonotonic nature of changes in the concentration of alloying elements and electrical conductivity. Various contributions to the Cu–0.6Cr–0.1Zr alloy hardening were analyzed. The analysis identified that the dispersion strengthening contribution plays the main role in the nonmonotonic change in the mechanical characteristics. The calculated data correlate with the obtained experimental results.