Microstructure and property of Cu-2.7Ti-0.15Mg-0.1Ce-0.1Zr alloy treated with a combined aging process

A combined aging process has been developed to improve the comprehensive properties of Cu-2.7Ti-0.15Mg-0.1Ce-0.1Zr alloy. This process involved pre-aging at an elevated temperature, cold rolling, and final aging at low temperature. The alloy treated by this process was found to have good electrical conductivity and super-high strength. As the alloy was solution treated at 850 °C for 2 h, aged at 450 °C for 8 h, then cold rolled with the reduction of 90%, followed by aging at 400 °C for 4 h, the hardness, tensile strength, yield strength, the elongation and electrical conductivity of the alloy were up to 340 Hv, 1035 MPa, 982 MPa, 3.1% and 20.1% IACS respectively. TEM observation revealed that the modulated structure and ordered Cu4Ti phases with coherent relationship with the matrix appeared during the pre-aging process. Cold rolling led to the formation of dense dislocation wall due to the dynamic interactions among the dislocations and precipitates. During the second stage of aging, the nano-scale precipitates formed in the pre-aging and the newly formed precipitates could effectively pin the dislocations formed in the cold rolling, the polygonization of recovery and recrystallization process could be retarded effectively. Therefore, the conductivity was enhanced without sacrificing the strength of the alloy when the second stage of aging was prolonged.