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Published online by Cambridge University Press: 01 February 2011
The heating rate dependencies of the glass transition temperature of the Ni65Nb35, Ni60Nb35Sn5, Ni59.35Nb34.45Sn6.2, Ni60(Nb40Ta60)34Sn6, and Ni57Fe3Nb35Sn5 metallic glass forming alloys were investigated with a differential scanning calorimeter (DSC). The relaxation time for each DSC experiment was plotted versus inverse temperature and a Vogel-Fulcher-Tamman (VFT) type relation was fitted to the data. The fragilities of the alloys were characterized with the fragility parameter, D*, and the VFT temperature, T0, which are the fit parameters from the VFT relation. It was found that for the binary alloy D* = 6.2, for the ternary alloys D* = 11.0, and that for the quaternary alloys D* was between 16.4 and 19.0. The D* increases monotonically as the number of components in the alloy is increased. This trend is also seen in Zr based alloys.