Phase separation and microstructure evolution of Zr₄₈Cu₃₆Ag₈Al₈ bulk metallic glass in the supercooled liquid region

The effect of annealing temperature on the microstructure evolution of Zr₄₈Cu₃₆Ag₈Al₈ bulk metallic glass was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Results show that the as-cast Zr₄₈Cu₃₆Ag₈Al₈ alloy by rapid solidication exhibits a typical characteristic of an amorphous structure. After annealed at 703 K for 20 min, a homogeneous amorphous matrix is separated into two different glassy phases, namely, phase separation occurs. Because phase separation structure will compete with the amorphous matrix during isothermal annealing, this structure is easily decomposed and transformed into the crystalline phases AlZr₂ and AlAg₃ with annealing temperature increasing. The microstructure of Zr₄₈Cu₃₆Ag₈Al₈ bulk metallic glass undergoes the local structure transformation, phase separation and nano-crystallization transformation during heat treatment in the supercooled liquid region, which implies that the microstructure of Zr₄₈Cu₃₆Ag₈Al₈ bulk metallic glass is sensitive to the annealing temperature. In addition, the formation of phase separation will accelerate the formation of nano-crystals.