Thermal Stability of Microstructure and Properties of Cu-0.5Cr-0.2Zr Alloy Subjected to ECAP and Cold Rolling

Abstract

Copper and copper alloys are widely used in engineering as structural materials because they have high electrical and thermal conductivity. In connection with the rapid growth of industry, special requirements are imposed on these materials, that is, they must withstand the contact mechanical loads without significant plastic deformation at elevated temperature and have stable high physical and mechanical properties. To improve the combination of strength, electrical conductivity, thermal stability, and wear resistance, low-alloyed Cu-Cr-Zr copper alloys have been subject to severe plastic deformation and aging. It the same time the analysis of the termo-stability of the formed ultrafine grained microstructure and properties is a topic task. In this work, a Cu-0.5Cr-0.2Zr (wt. %) alloy was quenched to form solid solution, equal channel angular pressed and cold rolled with following aging. The microstructure was studied, mechanical and electrical properties were also analyzed. The results showed that the ultimate strength of the Cu-Cr-Zr alloy increases with the degree of deformation at room temperature up to 630 MPa. Heat treatment at 450 ° C for 1 hour led to the precipitation of Cr and Cu5Zr particles, which increases the strength up to 660 MPa, which is 2.5 times greater than the initial state. At the same time, sufficient electrical conductivity of 70% IACS is maintained. The thermal stability of the microstructure and properties of the alloy are investigated. The reinforced alloy maintains stable the microstructure and microhardness at 450 ° C for at least 5 hours. The change in microhardness is no more than 10%. That is in agreement with the requirements of industry.