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 Ni70Nb15Y15 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.