Biaxial deformation behavior and formability of precipitation hardened ultra-fine grained (UFG) Cu-Cr-Zr alloy

The combined effects of ultrafine-grained (UFG) microstructure and precipitation on the formability and biaxial deformation behavior of a Cu-Cr-Zr alloy were investigated. The UFG microstructure formation results in good formability with an Erichsen index (Ei) of 4.05 mm compared to that of peak-aged coarse grained (CG) alloy (3.95 mm). Aging heat treatments increase strength and formability of the UFG alloy simultaneously. Biaxial deformation behavior is found to be dependent on the strain hardenability. Excellent strain hardenability of the CG alloy brought about higher punch displacement within the membrane stretching regime. However, deformation localization with the early onset of necking is evident in the UFG alloy. Subsequent aging treatments decrease deformation localization behavior of UFG alloy with increasing aging durations. Results also show that both grain refinement and aging increased the punch load due to enhanced strength. A linear relationship is generated based on punch load vs. punch displacement curve slope to predict ultimate tensile strength (UTS) with high accuracy. It is concluded that synergetic effect of UFG microstructure formation and subsequent aging provides a simple and effective procedure to produce Cu-Cr-Zr alloy for applications where balance of strength and formability are needed.