Evidence of structure relaxation prior to nanocrystallization in an Al-based metallic glass

An asymptotically decreasing signal is observed in the initial part of the isothermal DSC curves at 275, 285 and 290 °C of an Al85Ni5Y6Co2Fe2 metallic glass with a supercooled liquid region. We demonstrate that the monotonically decaying signal originates from the structural relaxation of the quenched glass, rather than from the growth of the quenched-in nuclei. At 285 and 290 °C, an exothermic peak overlaps with the structural relaxation, corresponding to the precipitation of nanometer-sized Al crystals.