Abstract The depth profile of the crystallized Metglas 2605, Fe 80B 20 metallic glass, as well as the process of crystallization have been studied. Crystallization of Fe 80B 20 Metglas was observed during continuous heating between 25 °C and 600 °C in situ. Micrographs and diffraction patterns which tracked the phase transformation were taken through the entire range of temperatures. The depth profile phase distribution for the crystallization of Fe 80B 20 was obtained from the quench side to the free side. The electron microscopy results showed that the crystallization occurs preferentially at the free side of the amorphous strip during all stages of crystallization.