Compression with oscillatory torsion applied after solution treatment and aging treatment of CuCr0.6 alloy for grain refinement: Microstructure, mechanical and electrical properties

Microstructure, mechanical properties and electrical conductivity of the CuCr0.6 alloy processed by compression with oscillatory torsion (COT) at room temperature were investigated. The COT processing was applied for the samples processed with the solution treatment followed by quenching into iced water at 1000 °C for 3 h and for the samples processed using the solution treatment followed by aging treatment at 500 °C for 2 h. Application of the solution and aging processes prior to the COT deformation results in the partial dissolution of Cr precipitates into the Cu matrix and precipitation of the coherent second phase precipitates, respectively. COT processing with different values of the total effective strain (εft) of 10, 20, 40 was introduced to the material. It was found that the presence of the second phase precipitates has a significant effect on the formation of the ultrafine grain (UFG) structure during the COT deformation. After the COT deformation with maximal effective strain value of εft = 40 of the samples processed by aging, the obtained grain size was about 300 nm and the high angle boundary fraction of about 30%. Application of the COT deformation at the effective strain value of εft = 40 for the samples after solid-solution treatment leads to the formation of a UFG microstructure with the average grain size of about 450 nm and the high angle boundary fraction of 13%. Formation of the more refined UFG structure and the presence the dispersed chromium precipitates in the samples after aging contributes to the enhanced ultimate tensile strength (UTS) of 521 MPa, with the electrical conductivity of 85% IACS, which are much higher than the corresponding values of solid-solution-treated samples prior to COT of 353 MPa and 40% IACS.