Isothermal nanocrystallization behavior of bulk metallic glass composites in supercooled liquid region

Bulk metallic glass composites （BMGCs） reinforced by micro- （spherical size of about 10 gin） and nano-sized （20-50 nm） A13Zr crystals were synthesized by copper mold suction casting method. The isothermal crystallization of Cu4oZr44AgsAls BMGCs in the super- cooled liquid region was studied by differential scanning calorimeter （DSC）, X-ray diffractometer （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The mechanisms for nucleation and growth of the crystalline phases precipitated in two-stage crystallization process and the effect of the isothermal treatment on the in situ crystalline phases were discussed. Results show that the BMGCs experience a primary crys- tallization process. Nano-sized A13Zr and Cul0Zr7 phases precipitate from the amorphous matrix successively. Fur- thermore, isothermal annealing has no effect on the pre- existing particles in the as-cast sample, which creates a new method to synthesize BMGCs strengthened by duplex crystalline phases with a large size difference. And the reinforced phase could also be dominated with intention if the as-cast BMGCs preparation and isothermal treatment process can be controlled more accurately.