Microstructure evolution of the interfacial phase in a melt-spun nanocrystalline Hf-Ni alloy

By using the melt-spinning technique, a nanocrystalline (NC) Hf11Ni89 alloy was prepared which is composed of a major nanophase of HfNi5 compound (wit h an average grain size of about 10 nm and an interfacial phase of a Ni(Hf) solid solution. The thermal stability and the microstructure evolution kin etics of the interfacial Ni(Hf) phase were characterized by means of magnet othermal analysis (MTA). Evident magnetic property changes were observed fo r the interfacial phase in the NC sample at temperatures far below the dete ctable grain growth temperature. corresponding to diffusion of Hf (depletio n) in the interfacial phase and the Ni solid-solution precipitation process from the supersaturated HfNi5 nanophase. Kinetic parameters such as charac teristic temperatures and activation energies were obtained for these micro structural evolution processes by using the quantitative MTA measurements d uring isochronal and isothermal annealing treatments. The kinetics of the H f depletion in the interfacial Ni(Hf) phase and the dimensionality of the N i precipitate are found to be sensitive to the annealing temperature.