Microstructural evolution and phase transformation kinetics of pulse-electroplated Ni-Cu-P alloy film during annealing

Ni-Cu-P alloy film of 4.0 wt%Cu and 10.1 wt%P was deposited on Cu substrate through pulse electroplating. Microstructures, morphologies and phases of the alloy films were studied. Phase transformation kinetics of the alloy films during the DSC annealing was also investigated. The results show that the as-deposited Ni-Cu-P alloy film is composed of an amorphous Ni(Cu,P) matrix in which 5 nm spherical Ni(Cu) grains are embedded. After the alloy film annealed at 673 K, Ni5P2 precipitates from the amorphous matrix; and at 773 K, Ni5P2 transforms into Ni3P, which is spherical and about 10 nm in diameter. Meanwhile, the nanocrystalline Ni(Cu) grains grow up to be regular hexagon and 60-70 nm in diameter. The activation energies related to the precipitation of Ni5P2 from the Ni(Cu,P) matrix and the phase transformation of Ni3P from Ni5P2 were deduced to be 178.3 and 238.4 kJ mol−1, respectively.