Effect of friction-stir processing on microstructure and mechanical properties of Cu-Cr-Zr-Y alloy

This study examined the effect of friction stir processing (FSP) on the microstructure and properties of a novel Cu-Cr-Zr-Y alloy. In addition, the microstructural aspects of doping Cu-Cr-Zr bronze with yttrium were considered. It was found that owing to the extremely low solubility of yttrium in copper, this alloying element was primarily concentrated in a secondary phase. Owing to the low melting point of the Y-rich phase, it precipitated as coarse inclusions and thus exerted only a minor influence on the material behavior. In contrast, FSP was found to be quite feasible for the thermomechanical processing of the Cu-Cr-Zr-Y alloy. Specifically, a single FSP pass resulted in a more than three-fold increase in strength characteristics and simultaneously provided a substantial enhancement in electrical conductivity. This effect was attributed to the formation of an ultrafine-grained structure and the precipitation of Cr-rich dispersoids within the stir zone. • Formation of triple-eutectic structure with low melting point in Cu-Cr-Zr-Y alloy. • Effective grain refinement and fragmentation of eutectic inclusions via FSP. • Low-temperature FSP promotes nanoscale Cr particle precipitation. • Threefold increase in strength and electrical conductivity after single FSP pass.