Overcoming the strength-conductivity trade-off in Cu–3Ti alloys via a pre-aging strategy

A Cu–3Ti alloy was prepared via the induction melting method, followed by thermomechanical treatment, including solution treatment, pre-aging, cold rolling and final aging. Pre-aging was applied to tailor the synergy between strength and electrical conductivity (EC) in Cu–3Ti alloys. The findings reveal that the microstructure of the as-cast Cu–3Ti alloy is composed mainly of α-Cu dendrites, with Ti-rich phases located in the interdendrite identified as Cu 3 Ti, β′-Cu 4 Ti, and β-Cu 4 Ti. After cold rolling followed by final aging, the microstructure of the alloy evolves into a fibrous structure, accompanied by the formation of numerous shear bands. Transmission electron microscopy revealed that a large amount of nano-β′-Cu 4 Ti precipitated in the Cu matrix during pre- and final aging, thereby significantly increasing both the strength and the EC of the alloy. As the pre-aging time increased (450 °C for 0–10 h), the EC of the Cu–3Ti alloys continuously increased, whereas the tensile strength first increased rapidly but then gradually decreased. Following solution treatment at 900 °C for 2 h, pre-aging at 450 °C for 6 h, cold rolling to 94% reduction and final aging at 450 °C for 1 h, the EC and ultimate tensile strength (UTS) of the Cu–3Ti alloy were 14.8% IACS and 1081.9 MPa, respectively, which are 21.8% and 24.9% greater than those of the alloy without pre-aging, respectively. The contributions of various strengthening mechanisms were also analyzed, and compared with the treatment without pre-aging, precipitation strengthening played a leading role, with the contribution increasing by 11% (PAG/6 h). This research contributes to the development of high-performance copper alloys by offering a new strategy to achieve a superior strength–conductivity combination.