Isothermal crystallization kinetics of Ni60Nb4o-xCrx,glasses

Isothermal crystallization kinetics of Ni₆₀Nb_40-xCr_x (x = 0, 5, and 13 at %) glasses was investigated by differential scanning calorimetry. It was possible to separate out the kinetics of formation of various phases which are obtained on crystallization of these glasses. The results are compared with the earlier investigations [1] in which the data were obtained by constant heating rate experiments. The crystallization of M-phase, Ni₃Nb and NbCr₂ phases could be described by Johnson-Mehl-Avrami kinetics. The activation energies for the formation of these phases were found to decrease in the same order. A decreasing activation energy with increasing transformed fraction (time) was also observed. The results are interpreted in light of the values obtained for Avrami exponents.