Crystallization behavior of low temperature pre-annealed Zr46.8Ti8.2Ni10Cu7.5Be27.5—bulk glass

During heat treatment of metallic bulk glasses at temperatures below the calorimetric glass transition temperature Tg, the glasses undergo microstructural alterations indicated by their thermal behavior as observed by DSC, but not discernible by X-ray diffraction (XRD). A reversible enthalpy recovery at Tg indicates a slow, reversible relaxation of the glass into a temperature dependent structural equilibrium state. After prolonged annealing times below Tg the crystallization is irreversibly affected, i.e. it starts at a lower temperature, takes a different pathway and ends up in a different crystalline microstructure. This behavior was studied in Zr46.8Ti8.2Ni10Cu7.5Be27.5—bulk glass (V4) after preceding long term annealing well below Tg=603 K by means of differential scanning calorimeter (DSC), XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and microhardness measurements.