Crystallization and Glass Forming Ability of Supercooled Pd-Cu-Ni-P Melt

Abstract

The thermal stability, GFA and crystallization behavior of a highly purified Pd₄₀Cu₃₀Ni₁₀P₂₀ supercooled liquid was examined. Under continuous cooling, the critical cooling rate for glass formation for the highly purified alloy is the same as that (0.100 K/s) for the fluxed ordinary alloy, though the magnitude of supercooling is enhanced by about 80 K upon by the purification treatment. The enhancement is presumed to result from the elimination or decrease of the quenched-in nuclei. The Time-Temperature-Transformation (TTT) diagram was constructed experimentally under isothermal annealing of the supercooled melt. The nose point in the TTT diagram is located at 683 K and 80 s. By utilizing the high thermal stability of the supercooled liquid, in-situ TEM observation was successfully carried out. In the isothermal annealing at 683 K, crystalline particle with a diameter of about 15 nm abruptly precipitated from the molten particle with a diameter of 40 nm and no significant grain growth was observed during further annealing. The incubation time was measured to be 3180 s. This value is much longer than that of the sample obtained by the HV/HT-DSC measurement. The difference between the two incubation times indicates that the nucleation is the event dominated by statistical probability.