Effect of ECAP processing on distribution of second phase particles, hardness and electrical conductivity of Cu-0.81Cr-0.07Zr alloy
(1. Institute of Science and Technology, Federal University of S？o Paulo, 330 Talim St., S？o José dos Campos, 12231-280, Brazil;
2. Institute for Metals Superplasticity Problems RAS, 39 S. Khalturin St., Ufa, 450001, Russia;
3. Ufa State Aviation Technical University, 12 K. Marx St., Ufa, 450008, Russia)
2. Institute for Metals Superplasticity Problems RAS, 39 S. Khalturin St., Ufa, 450001, Russia;
3. Ufa State Aviation Technical University, 12 K. Marx St., Ufa, 450008, Russia)
Abstract: The effect of equal-channel angular pressing (ECAP) processing at room temperature and 300 °C on the distribution of the second phase particles and its influence on hardness and electrical conductivity of the commercial Cu-0.81Cr-0.07Zr alloy were investigated. Microstructural characterization indicated that the area fraction of coarse Cr-rich particles decreased after ECAP processing. This reduction was attributed to the Cr dissolution induced by plastic deformation. The electrical conductivity of the alloy decreased by 12% after 4 ECAP passes at room temperature due to the increase of electrons scattering caused by higher Cr content in solid solution and higher density of defects in the matrix. These results were supported by the reduction of the Cu lattice parameter and by the exothermic reactions, during differential scanning calorimetry (DSC) analysis, observed only in the samples subjected to ECAP processing. Aging heat treatment after ECAP processing promoted an additional hardening effect and the complete recuperation of the electrical conductivity, caused by the re-precipitation of the partially dissolved particles. The better combination of hardness (191 HV) and electrical conductivity (83.5%(IACS)) was obtained after 4 ECAP passes at room temperature and subsequent aging at 380 °C for 1 h.
Key words: ECAP; Cu-Cr-Zr alloy; second phase particles; phase transition