Combined in-situ SAXS/WAXS and HRTEM study on crystallization of (Cu60Co40)1 − xZrx metallic glasses

► Cu -Co -Zr fulfills prerequisites to form a phase separated glass-glass composite. ► Cu -Co exhibits a positive enthalpy of mixing driving the phase separation. ► Even for (Cu60Co40)68Zr32, no indications for phase separation in as-quenched state. ► Since glassy state is metastable, crystallization processes are always competing. ► In-situ SAXS/WAXS and HRTEM reveals formation of very small crystallites (<2 nm).