Formation and crystallization of Zr-Ni-Ti metallic glass
摘要
The metallic Zr65 Ni25 Ti10 (mole fraction, %) glass has been fabricated by a single roller melt-spinning method. The glass forming ability(GFA) and thermal stability of the Zr65 Ni25 Ti10 melt-spun ribbons were investiga ted 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 (Trg) is 0. 506 and the supercooled liquid region (△Tx) 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 is observed that the meta stable FCC Zr2 Ni(Fd3m, α= 12.27 (A)) precipitated while annealing in the suppercooled region(615 K) and the stable BCT Zr2Ni(I4/mcm, α=6. 499 (A), c=5. 270 (A)) precipitated while annealing at higher temperature(673 K or 723K). The crystallines are on nanoscale, with grain size of 15 -30 nm. The reason for the precipitation of the different structural Zr2 Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order(MCSRO).