Abstract: The crystallization behavior and the structure of the electroless Ni68.6-Fe9.6-P21.8 deposit were studied by DSC and XRD. The results show that the as-plated deposit consists of amorphous phase, crystallizes into metastable Ni5P2(P3) and Fe-Ni(Im3m) at 367.6 ℃, and transforms into Ni3P(I-4) and FeNi3(Pm3m) at 499.2 ℃. Scanning electron microscopy was performed to observe the surface micromorphology of the as-plated deposit and the deposit heat-treated at 500 ℃. The heat-treated consists of many grains with diameters of 10～30 nm. The microhardness of the deposit increases with the increase of the annealing temperature up to 500 ℃, after which it decreases. The as-plated deposit almost has no magnetism, and its magnetic properties increase with the increase of annealing temperature, showing a rapid increase at above 600 ℃. The saturation magnetization and the coercive force increase greatly with the annealing temperature at above 400 ℃. The corrosion resistances of the as-plated deposit and the deposit heat-treated at 600 ℃ in w=3.5％ NaCl solution (pH 7.0) were investigated by mass loss tests and anodic polarization experiments. The results indicate that the as-plated deposit has a better corrosion resistance than that of the heat-treated deposit in this environment, and their anodic polarization behaviors are different. The above properties of the deposits were discussed from the structure and micromorphology of the deposits.

Key words: Electroless plating, Ni-Fe-P, Alloy, Heat treatment, Property