Atom Probe Studies of Supercooled Liquids

Abstract
Phase transformations in the supercooled liquid region (between T_g and T_cryst), prior to the onset of crystallization, in amorphous Pd-Ni-P alloys remain controversial. It has been previously proposed that the amorphous alloy decomposes into two amorphous phases prior to the crystallization reaction when annealed in the supercooled liquid region. Investigations by DSC, Mössbauer spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) small-angle X-ray scattering (SAXS) and atom probe field ion microscopy (APFIM) have since corroborated or refuted phase separation prior to crystallization in the supercooled liquid region of Pd-Ni-P alloys. The microstructural development during annealing in the supercooled liquid region of amorphous Pd₄₆Ni₃₆P₁₈, which is supposedly of phase-separating composition, is compared and contrasted with those of Pd₄₈Ni₃₂P₂₀ and Pd₄₀Ni₁₀Cu₃₀P₂₀. TEM showed that the as-quenched alloys were fully amorphous and APFIM analysis showed random solute distributions, typical of amorphous materials. Annealing in their respective supercooled liquid regions did not result in the formation of compositionally modulated microstructures prior to the onset of crystallization.