Crystallization and glass forming ability of supercooled Pd-Cu-Ni-P melt

The thermal stability, GFA and crystallization behavior of a highly purifie d Pd40Cu30Ni10P20 supercooled liquid was examined. Under continuous cooling , the critical cooling rate for glass formation for the highly purified all oy is the same as that (0.100 K/s) for the fluxed ordinary alloy, though th e magnitude of supercooling is enhanced by about 80 K upon by the purificat ion treatment. The enhancement is presumed to result from the elimination o r decrease of the quenched-in nuclei. The Time-Temperature-Transformation ( TTT) diagram was constructed experimentally under isothermal annealing of t he 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 a nnealing at 683 K, crystalline particle with a diameter of about 15 nm abru ptly precipitated from the molten particle with a diameter of 40 nm and no significant grain growth was observed during further annealing. The incubat ion 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 th e two incubation times indicates that the nucleation is the event dominated by statistical probability.