Precipitation behavior and properties change of Cu-3Ti-0.5Mg-0.5Sn alloy during two-stage cold rolling and aging treatment

The microstructural evolution of the Cu-3Ti-0.5Mg-0.5Sn alloy after the first and secondary cold rolling combined with aging treatments was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the mechanical properties and electrical conductivity of the designed alloy were tested after different aging times to determine the performance variations of the alloy during the two-step thermomechanical treatment. The results show that after the second cold rolling and aging treatment (Process II), the conductivity and tensile strength of the Cu-3Ti-0.5Mg-0.5Sn alloy were both effectively improved compared with those after the first cold rolling and aging treatment (Process I). The optimum process was determined to be 60 % cold rolling→aging at 380 °C for 6000 min →60 % cold rolling, followed by aging at 350 °C for 6000 min, resulting in a tensile strength of 1100 MPa and an electrical conductivity of 25.7 %IACS. Ti3Sn intermetallic compounds were formed, which reduced the Ti and Sn contents dissolved in the Cu matrix, thus enhancing the electrical conductivity of the alloy. Long-term, low-temperature aging promoted the formation of nanoscale α-Cu4Ti precipitates and maintained the multiplication of dislocations.