Formation and crystallization of Zr-Ni-Ti metallic glass

The metallic Zr₆₅Ni₂₅Ti₁₀ (mole fraction, %) glass has been fabricated by a single roller melt-spinning method. The glass forming ability (GFA) and thermal stability of the Zr₆₅Ni₂₅Ti₁₀ melt-spun ribbons were investigated by using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) in the mode of continuous heating. It is shown that the reduced glass transition temperature (T_rg) is 0.506 and the supercooled liquid region (ΔT_x) is 30 K. Two exothermic peaks were observed in the DSC curves of the as-quenched ribbon, which indicates that the crystallization process undergoes two different stages. The phase transformation during the isothermal annealing was investigated by X-ray diffraction (XRD) and transmission electronic microscope (TEM). It was observed that the meta-stable FCC Zr₂Ni(Fd3m, a=12.27 Å) precipitated while annealing in the suppercooled region (615 K) and the stable BCT Zr₂Ni (I4/mcm, α=6.499 Å, c=5.270 Å) precipitated while annealing at higher temperature (673 K or 723 K). The crystallines are on nanoscale, with grain size of 15-30 nm. The reason for the precipitation of the different structural Zr₂Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order (MCSRO).