Formation of Icosahedral Phases and Bulk Metallic Glasses in (Zr_(65)Al_(10)Ni_(10)Cu_(15))_(100-x)Nb_x Alloys

摘要

The discovery of metastable I-phase in the devitrification processes of Zr-based bulk metallic glasses (BMGs) has activated intense research interests on the structural relation between the I-phase and Zr-based BMGs and on the underlying mechanisms governing their formations [1]. Usually, the precipitation of nanometer-scaled I-phase is observed in the first exothermic reaction of these Zr-based BMGs, covering a broad compositional span. Whether the I-phase is the only crystallization counterpart remains to clarify in all these compositions, which is the highest priority of the crystallization mechanism. On the other hand, few of the investigations have been made on the formation of I-phase during the liquid cooling down path of these alloys. In the present work, the formation of I-phases and BMGs is to be explored in the (Zr_(65)Al_(10)Ni_(10)Cu_(15))_(100-x)Nb_x alloy system. The compositional dependence of their formations in casting is to be examined. Devitrification of the metallic glasses is also studied, putting an emphasis on the structural evolution and the accompanied composition change.