Fluctuation electron microscopy of Al-based metallic glasses: Effects of minor alloying addition and structural relaxation on medium-range structural homogeneity

Al-based metallic glasses with relatively high glass-forming ability have been studied using fluctuation electron microscopy (FEM). These glasses exhibited well-defined glass transition and remained fully amorphous throughout the FEM experiments. Peaks were observed in the normalized intensity variance curves, evolving with sample composition and thermal history, while diffraction patterns remained identical. Specifically, minor alloying of Co into the Al ₈₅Ni₅Y₁₀ glass improved its medium-range homogeneity. This is in accord with, and partly explains, the increase in the glass-forming ability. After annealing of Al₈₅Ni₅Y ₈Co₂ below its glass transition temperature, FEM suggests structural homogenization or intensified medium-range fluctuations, depending on the annealing temperature. Such dissolution versus growth of quenched-in heterogeneity accompanying structural relaxation was not detectable using other techniques.