The evolution of Cr-rich precipitates in Cu-0.25Cr-0.03Ti alloy induced by trace Ti element
Yanjun Zhou, Yibo Du, Xiaowen Peng, Kexing Song, Shaodan Yang, Jingzhao Yang, Qianqian Zhu, Yahui Liu, Chaomin Zhang, Siyu He
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.