ZR-Y BASE AMORPHOUS-ALLOYS WITH 2 GLASS TRANSITIONS AND 2 SUPERCOOLED LIQUID REGIONS

Two-stage glass transitions combined with two supercooled liquid regions were observed before the completion of crystallization for Zr60-xYxAl15Ni25 amorphous alloys containing 15-35 at.% Y. The phase transition of these amorphous alloys on heating takes place in the sequence amorphous solid, first-stage reactions of glass transition, supercooled liquid and crystallization, and then the second-stage reactions of glass transition, supercooled liquid and crystallization. The first-stage reactions are due to a Y-rich Y-Al-Ni.amorphous phase, and the remaining Zr-rich Zr-Al-Ni amorphous phase causes the second-stage reactions. The first-stage exothermic reaction results from the homogeneous precipitation of crystalline particles with a size of about 3 nm. The remaining amorphous phase, which coexists with the nanoscale Y-rich crystalline particles, exhibits a large temperature range of supercooled liquid of up to 104 K, and has optimum structural and bonding states in which no extra consistent atoms with a weak bonding nature are included.