Microstructure and properties of Cu-Cr-Nb alloy with high strength, high electrical conductivity and good softening resistance performance at elevated temperature

Cu-0.47Cr-0.16 Nb (wt%) alloys were designed and prepared, and the microstructures of the Cu-Cr-Nb alloy were investigated using transmission electron microscopy and three-dimension atom probe tomography technique. After homogenizing at 950 °C for 4 h, cold rolling by 80% reduction, then aging at 450 °C for 30 min, the micro-hardness, electrical conductivity, tensile strength, yield strength and elongation of the alloy were up to 150 HV, 89.1%IACS, 453 MPa, 443 MPa and 11.4%, respectively. The tensile strength / elongation of the alloy approached 399 MPa / 22.9% as test at 200 ℃, 334 MPa / 14.8% for 300 ℃, and 282 MPa / 12.3% for 400 ℃, respectively. The Cr2Nb phase with an average size of 700 nm and Nb phase with an average size of 500 nm formed during the solidification process, while the nano-scale Cr-rich phases precipitated from the solid solution during the aging process. The sizes of Cr2Nb and Cr-rich phases were close to each other during aging. These precipitates located in the grain and sub-grain boundary could effectively pin the movement of boundary, resulting in a high strength of the alloy at the elevated temperature. The addition of Nb can promote the precipitation of Cr from the solid solution during aging, thus both strength and electrical conductivity of the alloy were improved.