The Influence of Zirconium on the Low-Cycle Fatigue Response of Ultrafine-Grained Copper

摘要

This article reports on the influence of zirconium (Zr) addition (0.17 wt pct) on the cyclic stability of ultrafine-grained (UFG) oxygen-free high-conductivity (OFHC) copper (Cu) of originally high (99.995 wt pct) purity processed via equal-channel angular extrusion (ECAE). Systematic low-cycle fatigue (LCF) tests accompanied by microstructural investigation revealed that a Zr addition substantially affects the cyclic stability of UFG Cu, such that longer fatigue lives, notable cyclic hardening, and higher stress ranges were attained in the LCF regime. This significant improvement of the fatigue properties of OFHC Cu by the addition of Zr is attributed to the Cu-Zr precipitates and impurities, effectively limiting the mobility of the grain boundaries and additional work hardening imposed by the precipitates. In addition, the strain-amplitude and strain-rate dependencies of the cyclic stability of Zr-added UFG Cu were investigated in detail, where the UFG Cu-Zr alloy exhibits an expressively lesser dependency as compared with the pure UFG Cu. The current results offer new insight into the improvement of the cyclic stability of UFG Cu and other UFG materials, and provides a venue for their utility in a broader range of applications demanding enhanced cyclic deformation response and stability.