Precipitation behavior and properties change of Cu–3Ti–2Ni alloy during aging process

Abstract

The microstructural evolution of Cu–3Ti–2Ni alloy under primary and secondary cold rolling combined aging was investigated through various characterization techniques including transmission electron microscopy (TEM), scanning electron microscope (SEM), and X-ray diffraction (XRD). Additionally, the electrical and mechanical properties during different stages of aging were examined to reveal the organizational changes and performance variations of Cu–3Ti–2Ni alloy under primary and secondary aging. This study revealed that the alloy exhibited optimal primary aging performance at 450 °C for 4 h, with a strength of 954 MPa and an electrical conductivity of 21.5 %IACS (International Annealed Copper Standard for Conductivity). In comparison to primary aging, both strength and electrical conductivity were effectively improved under secondary aging conditions. The optimum secondary aging process was determined to be aging at 400 °C for 3 h, resulting in a strength of 1133 MPa and an electrical conductivity of 24.2 %IACS. During the aging process, the matrix witnessed the formation of numerous elliptical disc-shaped NiTi and Ni3Ti phases. Notably, the interface of NiTi phases exhibited a stronger coherency effect compared to Ni3Ti. β′-Cu4Ti precipitated uniformly within the matrix during aging, enhancing the alloy's strength. A recovery and recrystallization process occurred during aging, leading to the formation of sub-grains within the matrix.