Interface evolution of Cu–Ni–Si/Al–Mg–Si clad composite wires after annealing

Interface microstructures of Cu–Ni–Si/Al–Mg–Si clad composite wires during isothermal annealing from 623 to 773 K were investigated. The composite wires were fabricated by a drawing process. The evolution of intermetallic compounds (IMCs) was analyzed. A continuous IMCs layer forms only after annealing for 1 min, which may be due to more IMCs nucleation points generated by deep drawing process. IMCs consist of Al₄Cu₉, AlCu and Al₂Cu identified by energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The growth activation energies of total IMCs, Al₂Cu, AlCu and Al₄Cu₉, are 98.8, 69.4, 101.3 and 137.1 kJ·mol⁻¹, respectively. The higher growth activation energy of Al₄Cu₉ results in the higher growth rate under high temperature. However, the average interdiffusion coefficient for each IMC calculated by Wagner method shows that interdiffusion in Al₂Cu and AlCu is more active than that in Al₄Cu₉. The higher growth rate of Al₄Cu₉ may be caused by the long concentration range.