Aging process and strengthening mechanism of Cu-Cr-Ni alloy with superior stress relaxation resistance

With the development trend of connectors to high-current and high-temperature service, copper alloy connectors are required to have superior stress relaxation resistance. In this work, the optimal aging parameter was explored via stress relaxation resistance, strength, microhardness, and conductivity. And the strengthening mechanism of stress relaxation was investigated through the TEM and EBSD microscopic characterization. The results show that the Cu-Cr-Ni alloy reached the peak aging state under 450 °C for 1h and obtained excellent properties. Especially, the percentage of residual stress in the relaxation test reached 93.1%. The microhardness associated with aging strengthening showed a positive correlation with yield strength and stress relaxation resistance. Then the microhardness after aging can be used as a simple evaluation index of stress relaxation resistance. The Cu-Cr-Ni alloy with superior stress relaxation resistance is mainly related to dislocation strengthening, second phase strengthening, and the coexistence of spinodal decomposition and ordering.