Effect of Ni content on crystallization of metallic Zr–Cu–Ni glass

Abstract

Employing the X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques, the effect of Ni content on crystallization behavior of metallic Zr 70Cu 30− x Ni x ( x=5, 10 and 15) glasses has been investigated. It is found that all the DSC traces of metallic Zr 70Cu 30− x Ni x ( x=5, 10 and 15) glasses display two exothermic peaks, indicating that the crystallization processes of metallic Zr 70Cu 30− x Ni x ( x=5, 10 and 15) glasses proceed via a double stage mode. It is observed that the two exothermic peaks in the DSC scans of metallic Zr 70Cu 25Ni 5 and Zr 70Cu 15Ni 15 glasses overlap, implying that the crystallization processes of these two metallic glasses proceed through the almost simultaneous precipitation of crystalline phases. As for the metallic Zr 70Cu 20Ni 10 glass, the exothermic peaks in the DSC curves are more separated than those of the metallic Zr 70Cu 25Ni 5 and Zr 70Cu 15Ni 15 glasses, indicating that the crystallization products of metallic Zr 70Cu 20Ni 10 glass precipitate in sequence. To explain these experimental results, a micromechanism for crystallization of metallic Zr 70Cu 30− x Ni x ( x=5, 10 and 15) glasses is suggested. In addition, the origin of the high stability of the f.c.c.-Zr 2Ni phase is also interpreted from the viewpoint of local activation energy for crystallization.