Phase Equilibria and Thermal Stability of Pd-Cu-Ni-P Alloys

Abstract

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.