Nanocrystallization of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 metallic glass

The nanocrystalline microstructure evolution of Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10.0}Be{sub 22.5} metallic glass has been studied by three-dimensional atom probe (3DAP), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). Nanoscale icosahedral phase (i-phase) precipitates from a single amorphous phase by isothermally annealing at slightly above the glass transition temperature, T{sub g}, followed by the formation of Be{sub 2}Zr and CuZr{sub 2} phases. A uniform featureless amorphous-like contrast was observed by TEM before the i-phase nanoparticles were detected. 3DAP analysis results have convincingly shown that the decomposition occurs only when i-phase nanoparticles were observed by TEM. The Ti-rich and Be-depleted region that appears in the early stage annealing is due to the partitioning of the alloying elements accompanied by the crystallization reaction. No evidence for prior decomposition in the amorphous state was obtained.