ATOM-PROBE STUDIES OF SUPERCOOLED LIQUIDS

Phase transformations in the supercooled liquid region (between T-g an d T-cryst), prior to the onset of crystallization, in amorphous Pd-Ni- P alloys remain controversial. It has been previously proposed that th e amorphous alloy decomposes into two amorphous phases prior to the cr ystallization reaction when annealed in the supercooled liquid region. Investigations by DSC, Mossbauer spectroscopy, X-ray diffraction (XRD ), transmission electron microscopy (TEM) small-angle X-ray scattering (SAXS) and atom probe field ion microscopy (APFIM) have since corrobo rated or refuted phase separation prior to crystallization in the supe rcooled liquid region of Pd-Ni-P alloys. The microstructural developme nt during annealing in the supercooled liquid region of amorphous Pd46 Ni36P18, which is supposedly of phase-separating composition, is compa red and contrasted with those of Pd48Ni32P20 and Pd40Ni10Cu30P20. TEM showed that the as-quenched alloys were fully amorphous and APFIM anal ysis showed random solute distributions, typical of amorphous material s. Annealing in their respective supercooled liquid regions did not re sult in the formation of compositionally modulated microstructures pri or to the onset of crystallization.