Enhanced combination of mechanical properties and electrical conductivity of a hard state Cu-Cr-Zr alloy via one-step friction stir processing

Abstract

How to coordinate the strength, ductility and electrical conductivity of Cu-Cr-Zr alloys has always been a difficult problem. Unlike most of previous reports on processing soft state (solution state) alloys, in the present study, a hard state (aged state) Cu-Cr-Zr alloy was subjected to one-step friction stir processing (FSP) at room temperature with more attentions paid to the evolution of grains and precipitates, and their effects on the mechanical and electrical properties. The results showed that the precipitates played a key role in grain refinement, and ultrafine grains (UFG) with an average size of 250 nm were produced after FSP. Many fine precipitates (average size of 3.1 nm) were uniformly distributed in the grains, neither dissolved nor obviously coarsened. Excellent comprehensive properties of high tensile strength (702 MPa), good elongation (16%) and electrical conductivity (74.3% IACS) were achieved in the FSP sample. Furthermore, this one-step FSP method does not need subsequent aging treatment which is indispensable for conventional processing methods, providing a simplified and efficient method for improving the performance of Cu-Cr-Zr alloys.