Spinodal decomposition of Ni–Nb–Y metallic glasses

Phase-separated Ni-Nb-Y metallic glasses were prepared by rapid quenching from the melt. The early stages of decomposition were characterized in Ni-Nb-Y alloys with Ni contents of more than 60 at.%. Strongly correlated chemical fluctuations with a nanometer length scale were found to exist in the as-quenched state. The observed fluctuation lengths range from 5 to 12 nm, depending on the actual composition of the glass. The 'frozen-in' early stages of decomposition occur in the deeply undercooled melt due to the reduction in the critical temperature of liquid-liquid phase separation with Ni content. Annealing of the phase-separated Ni{sub 70}Nb{sub 15}Y{sub 15} glass below the crystallization temperature leads to an increase in the amplitude of the fluctuations. However, the wavelength was unchanged, which provides evidence for the spinodal character of the decomposition.