On the phase evolution and dissolution process in Cu-Cr alloys deformed by high pressure torsion

Normally immiscible 57 wt% Cu–43 wt% Cr compounds were mechanically alloyed by means of high pressure torsion with large and controllable strains. A strain-saturated state in 57 wt% Cu–43 wt% Cr bulk was achieved after 100 rotations deformation (effective strain 1360), with a stable grain size of 13.7 nm and largest solubility of 32 wt% Cu in Cr matrix. The phase fraction change between face-centered cubic and body-centered cubic due to Cu dissolution during continuous deformation was captured and accurately calculated, indicating a negative exponential phase change mode. A phenomenological dissolution mechanism based on the kinetic competition between mixing under sustained external forcing and thermal diffusion induced decomposition was proposed, which was well compliant with the phase evolution observed from experimental results.