Phase equilibria and thermal stability of Pd-Cu-Ni-P alloys

The critical cooling rate for glass formation in undercooled Pd-Cu-Ni-P alloys with compositions around Pd₄₀Cu₃₀Ni₁₀P₂₀ was found to have strong composition dependence. To clarify the compositional effect of thermal stability, phase equilibria of the Pd-Cu-Ni-P alloys were examined. The microstructural evolutions under various annealing conditions were evaluated using various microstructural characterization techniques including XRD, SEM, EDS and TEM. The major phases in the composition at a temperature of 770 K, which is slightly lower than the eutectic temperature consisting of Cu₃Pd, Ni₂Pd₂P, Cu₅Pd₃P₂, and Pd₂₉Cu₁₉Ni₂₈P₂₄. Coarse dendritic structures were also observed in the off-eutectic alloys. Based on the present results, the composition effect on the thermal ability of Pd-Cu-Ni-P alloys is discussed.