Effect of Zn addition on the crystallization process in Zr 65Al 7.5Ni 10Cu 17.5 metallic glass

Abstract

Zr 65Al 7.5Ni 10Cu 12.5Zn 5 and Zr 65Al 7.5Ni 5Cu 17.5Zn 5 metallic glasses, which were obtained by adding Zn to the well-known glass-former Zr 65Al 7.5Ni 10Cu 17.5, were prepared by a melt-spinning method and the crystallization process was studied by differential scanning calorimetry (DSC), X-ray diffraction and transmission electron microscopy. Two exothermic peaks were observed in the DSC curves. The low temperature one corresponds to the simultaneous precipitation of an icosahedral quasicrystalline phase (I-phase) and the face centered cubic Zr 2Ni (FCC–Zr 2Ni) phase in the Zr 65Al 7.5Ni 10Cu 12.5Zn 5 alloy. The initial precipitate for the Zr 65Al 7.5Ni 5Cu 17.5Zn 5 alloy is a single I-phase. Since an I-phase does not occur in the crystallization process of Zr 65Al 7.5Ni 10Cu 17.5 metallic glass, the present results demonstrate that the addition of Zn is effective in promoting the precipitation of an I-phase, in addition to the previously reported noble metals. Further annealing leads to the precipitation of other stable crystalline phases, indicating the metastable character of the I-phase and the FCC–Zr 2Ni phase. The reason for the change in the crystallization process caused by the addition of Zn was discussed on the basis of the chemical affinity and atomic radius of the constituent elements.