Development of High-Strength and High-Electrical Conductivity Cu–Zr Alloy Through Friction Stir Processing

Abstract

Friction stir processing (FSP) is a solid-state processing technique to enhance the surface properties of the metallic materials. The present study aims to improve the surface mechanical and wear properties of Cu–0.18wt.%Zr alloy through FSP without deteriorating its electrical conductivity behavior. The Cu–Zr alloy was friction stir processed at a constant tool rotation speed of 600 rpm and by varying the tool travel speed from 50 to 200 mm/min. The specimens were extracted from the stir zone to characterize its microstructure, mechanical properties and wear behavior. It was observed that the average size of grains in stir zone decreased from 40.5 to 4.6 µm with the increase in tool travel speed, whereas hardness of the processed specimens increased from initial 70 to 99 Hv. The coefficient of friction was decreased from 0.4 to 0.07 (µ) as travel speed increased. Consequently, the wear resistance of the processed samples increased with the travel speed. The change in electrical conductivity, as measured using eddy current technique, was noted to be insignificant in the processed specimens, i.e., it decreased to 77.4% IACS from its initial 78.2% IACS. Hence, the objective of improving the mechanical and wear resistance properties of Cu–Zr alloy was achieved without impairing the electrical conductivity by friction stir processing. The results suggest that friction stir processing can be effectively used to improve the wear behavior of high-strength and high-electrical conductivity alloys.