Nano-crystallization Studies on Cobalt containing Bulk Metallic Glasses

Abstract

The proposed project explores the addition of cobalt with Zr-Al-Co-Ni-Cu BMG. An attempt will be made to produce nano crystalline/quasicrystalline based composites in amorphous alloys through the process of crystallization. Few selected compositions from two sets of Zr-based alloys will be considered. The general compositions of two sets are as Zr58-xAl12CoxNi10Cu20, with0<x<10; Zr70Al10Cu11Ni9-xCox, with 0<x<5. The alloys from the first set will produce nanocrystalline embedded glass after suitable treatment. The second composition is expected to produce nanoquasicrystalline embedded glass, as Zr70Al10Cu11Ni9 had produced quasicrystalline phase from primary crystallization of Zr6NiAl2. The Cobalt addition will be studied in both the compositions in terms of crystallization with the help of transmission electron microscopy. Alloy buttons will be remelted using induction furnace to maintain the homogeneity of the alloy composition. Melting will be done in an inert atmosphere. Recrystallised alumina crucibles will be used to prevent contamination from the crucible side. Graphite will be used as susceptor for coupling to alumina crucibles during melting. 3 The alloy buttons will be subjected to rapid solidification. The standard melt-spinning technique will be followed to get rapidly solidified foils. Rapidly solidified foils will be produced from the amorphous alloys. They will be heat treated to get nanocrystals/nanoquasicrystals in the amorphous matrix. The properties of as cast and rapidly solidified foils will be characterized in steps by using XRD, DSC and TEM. XRD will be done to identify possible phases present in the bulk specimens. DSC studies will be carried out to know the temperature range for crystallization. The TEM studies are needed to know the evolution of fine microstructures and to know their crystallographic features. We may also explore the possibility of characterizing crystalline/amorphous interfaces. The possibility of formation newer phase(s) will also be considered.