Grain refinement kinetics and strengthening mechanisms in Cu-0.3Cr-0.5Zr alloy subjected to intense plastic deformation

摘要

The ultrafine-grained microstructures, mechanical properties and electrical conductivity of a Cu-0.3%Cr-0.5%Zr alloy subjected to equal channel angular pressing (ECAP) at a temperature of 400 ℃ to a total strain of 1, 2, and 4 were investigated. The ultrafine-grained microstructure resulting from progressive increase in the misorientations of strain-induced low-angle boundaries during the multiple ECAP process is considered as a type of continuous dynamic recrystallization. The multiple ECAP process resulted in substantial strengthening of the alloy. The yield stress of CuCrZr alloy in the initial solution treated condition (ST) increased from 65 MPa to 476 MPa after four ECAP passes at 400 ℃. For the aged condition (AT), the yield stress increased from 170 MPa to 511 MPa after four passes. The strengthening was attributed to the grain refinement and high dislocation densities evolved via large strain deformation. Bacon-Kocks-Scattergood modification of the Orowan model is sufficient for acceptable description of the precipitation hardening of AT specimens during ECAP processing; this finding is in excellent agreement with the experimental data. The discrepancy between the experiment and model for ST specimens disappears after taking into consideration additional precipitating of the supersaturated solid solution during preheating and ECAP processing.