Evolution of electric resistivity of iron and boron based amorphous alloys at crystallisation

The electric resistivity of the iron and boron based (Fe 80 Si 6 B 14 , Fe 76.2 Ni 3.8 Si 6 B 14 , Fe 78.5 Ni 1 Mo 0.5 Si 6 B 14 ) metallic glasses (MGs) was investigated in the temperature range 300-900K under an argon atmosphere by the four-probe method. The heating rate was varied from 2 K min -1 up to 11 K min -1 . The character of the temperature dependence of resistivity, p(T), for all samples under study within the range of the stability of amorphous structure was found to be linear, which is typical for a transition metal-metalloid MG. The form of p changed when MGs doped with nickel and molybdenum were analysed within the frame of the modified Ziman model. A change in the p(T) curves was observed at T > 700K because of the structural transformation to a crystalline state. In the precrystallisation temperature range, p changed nonlinearly, presumably because of structural relaxation of the MGs. The character of p changes at the crystallisation point, thus demonstrating the mechanism of primary crystallisation. The crystallisation kinetics were studied by the Kissinger method. The values of activation energy, E a , are in good agreement with those obtained from isothermal measurements and the Avrami equation (E a = 325 and 300 kJ mol -1 , respectively, for Fe 80 Si 6 B 14 ). In addition, the value of E a exhibited a tendency to rise when the MGs were doped with an additional component.