Phase transformation in Cu–Cr–Zr–Mg alloy

After solid solution treatment, the effects of aging processes on the microstructure and electrical conductivity of Cu–Cr–Zr–Mg lead frame alloy were investigated in order to determine the phase transformation and the time–temperature-transformation (TTT) behavior. The results show that aged at 470 °C the fine precipitation of an ordered CrCu2(Zr,Mg) phase is found in copper matrix as well as fine Cr and Cu4Zr, aged at 550 °C the phase CrCu2(Zr,Mg) is decomposed into Cu4Zr and Cr phase, aged at 600 °C the precipitates is bcc Cr only. The phase transformation kinetics equation was deduced from the Avrami empirical formula based on the linear relationship between the electrical conductivity and the volume fraction of the phase transformation.