Development of high strength and high electrical conductivity Cu-Cr-Zr alloy through friction stir processing

Abstract

Abstract Friction stir processing (FSP), a solid-state materials processing technique, is an effective method to modify the surface properties of metallic materials. In the present study, an effort has been made to improve the hardness and wear resistance of Cu–0.62 %Cr–0.11 %Zr alloy through FSP. Single-pass friction stirring was carried out by fixing the tool rotational speed as 600 rpm and by varying the tool traverse speed from 50 to 200 mm/min in steps of 50 mm/min. Samples were extracted from the stir-zone regime to characterize their microstructure, hardness, wear-resistance and electrical conductivity. It is observed that with an increase in tool traverse speed, the grain size of the stir zone decreases from 38 μm to 5 μm. At the same time, the Vicker’s hardness of the friction stir processed samples improved from initial 71VHN to 95VHN. A significant reduction in the coefficient of friction (CoF) noted after processing, and it continuously decreased from 0.4 to 0.12 as traverse speed increased. Consequently, the wear rate of the processed samples gradually decreased as traverse speed increased. The peak shift seen in X-ray patterns of processed specimens suggested the presence of residual strain in the processed zone. The electrical conductivity was measured applying the eddy current method. Conductivity decreased from 84 %IACS to 81.5 %IACS. Hence, the intent of improving the wear resistance and hardness of the Cu-Cr-Zr alloy attained without deteriorating the electrical conductivity by FSP. The results suggest that FSP can be successfully used to enhance the wear and mechanical properties of the high strength and high electrical conductivity Cu-Cr-Zr alloys.