Effect of precipitation on mechanical and wear properties of ultrafine-grained Cu-Cr-Zr alloy

The effect of an ultrafine-grained (UFG) microstructure and subsequent aging treatment on the mechanical and wear behavior of a Cu-Cr-Zr alloy was investigated. The results indicate that the precipitates dispersed within the UFG matrix significantly enhance the strain hardening, resulting in improvement of hardness, strength and wear resistance of the alloy, without notably sacrificing the elongation to failure and electrical conductivity, due to the combined effect of grain refinement and precipitation. The wear behavior of Cu-Cr-Zr alloy was found to be strongly dependent on its strength and hardness. The minimum weight loss (or the highest wear resistance) was obtained when the sample was processed by equal channel angular extrusion (ECAE) through an additional aging treatment, as this resulted in ultra-high strength and hardness. The wear results also indicate that the wear behavior of Cu-Cr-Zr alloy in all processing conditions is consistent with the Archard approach. Complex wear mechanisms such as adhesive, oxidative and abrasive wear, and delamination were found to be operative in the differently processed Cu-Cr-Zr alloys. It is to be concluded that the use of a two-step process, the first resulting in an UFG microstructure and a subsequent aging treatment provides a simple and effective procedure for extraordinary increase in strength, hardness and wear resistance of Cu-Cr-Zr alloys without modification of the chemical composition.