High-throughput determination of the interdiffusion coefficients in fcc Cu–Ni–Al–Zn alloys

Nine solid state Cu–Ni–Al–Zn quaternary diffusion couples were prepared, from which the concentration distributions of Cu, Ni, Al and Zn at 1123, 1173, and 1223 K were determined by using the electron probe microanalyzer (EPMA) technique. Utilizing the measured concentration profiles, the mobilities in fcc Cu–Ni–Al–Zn system were obtained, from which the interdiffusion coefficients were determined in a high-throughput manner with numerical inverse method. It showed that the main interdiffusivities satisfy D˜ZnZnCu>D˜AlAlCu>D˜NiNiCu over the investigated composition and temperature ranges. The influences of individual components on the diffusion rates were evaluated based on the determined interdiffusivities. In addition, three-dimensional main interdiffusion coefficient maps were constructed. The effects of composition on the main diffusion coefficients were analyzed, showing that D˜AlAlCu and D˜ZnZnCu increase with the increasing Al and Zn additions but decrease with increasing Ni content, while D˜NiNiCu has a more complex trend as the concentrations of Al, Ni and Zn change. According to the obtained diffusion coefficients, ways to optimize the temperature and time during homogenization heat treatment of different series of Cu–Ni–Al–Zn alloys were determined.