Suppression of discontinuous precipitation by Fe addition in Cu–Ti alloys

Cu–Ti alloys are a kind of elastic copper alloys with excellent comprehensive properties. They are often used in electronic and electrical fields. However, discontinuous precipitation may occur during the preparation process of Cu–Ti alloys, and they can lead to the significant deterioration of mechanical properties. To solve this problem, three Cu–Ti alloys with various Fe contents (Cu–2.7Ti, Cu–2.7Ti–0.1Fe and Cu–2.7Ti–0.2Fe) were designed and prepared in this paper to investigate the effects of Fe on the discontinuous precipitation. The results showed that after aging at any given aging time and temperature, the area fraction of cellular structure decreased with the increase of Fe content. The addition of Fe into Cu–Ti alloys resulted in Fe doping in β'–Cu₄Ti phase and β–Cu₄Ti phase. For 450 °C/144 h-aged Cu–2.7Ti–0.2Fe alloy, the Fe content in β'–Cu₄Ti phase and β–Cu₄Ti phase was 1.59 at% and 0.90 at%, respectively. The tensile tests showed that under the same aging treatment conditions, Cu–2.7Ti–0.2Fe alloy possessed better mechanical properties. First-principles calculation confirmed that the thermodynamic stability of β'–Cu₄Ti phase was enhanced by decreasing its cohesive energy through Fe doping. At the same time, the enthalpy of formation of β–Cu₄Ti phase was generally increased by Fe doping, making it difficult to generate. In short, Fe addition in Cu–Ti alloys suppressed discontinuous precipitation by Fe doping in the precipitates and helped to improve mechanical properties.