The evolution of Cr-rich precipitates in Cu-0.25Cr-0.03Ti alloy induced by trace Ti element

Abstract

In this paper, the prepared Cu-0.25Cr alloy and Cu-0.25Cr-0.03Ti alloy strips were treated with aging at 490 °C for different holding time. The electrical conductivity and the yield strength of the alloy were tested. The morphology, size, spacing and phase structure of Cr-rich precipitates in the copper matrix were observed by TEM. The results show that the evolution rule of Cr-rich precipitates in Cu-0.25Cr alloy is as follows: supersaturated solid solution→G. P region (Cr atom-rich region)→ Cr-rich precipitates with fcc structure→Cr-rich precipitates with ordered bcc structure. The precipitates of peak aged Cu-0.25Cr alloy consist of fcc Cr-rich precipitates and ordered bcc Cr-rich precipitates. The electrical conductivity and the yield strength is 93.5%IACS and 178 MPa, respectively. The strengthening mechanism is mainly attributed to the synergistic effect of dislocation shear and dislocation bypass. Compared with Cu-0.25Cr alloy, the yield strength of Cu-0.25Cr-0.03Ti alloy at peak aging state increases by 31.5%, while the electrical conductivity remains at 82.4%IACS. The great increase in strength is mainly attributed to the refinement of bcc Cr-rich precipitates by adding trace Ti element. The addition of Ti promotes the nucleation of Cr-rich precipitates and refines the Cr-rich precipitates of bcc structure. The interaction mechanism is that there is a strong mutual attraction between Ti and Cr atoms, which promotes the formation of clusters between Ti and Cr. This research results can provide a theoretical basis for the development of copper alloy for high-performance electrical connectors in aerospace, new energy vehicles and other fields.