Viscous-flow behavior of amorphous Co69Fe4.5Nb1.5Si10B15 alloys

The viscous-flow behavior of amorphous Co69Fe4.5Nb1.5Si10B15 alloys has been investigated. Thermomechanical analysis experiments showed effective viscosity decreasing monotonically with increasing temperature until steady-state viscous-flow temperature (Tvs), where the effective viscosity of the ribbon sample showed a minimum but increased after passing through that point. Annealing-induced changes of the free-volume fraction decreased with increasing temperature. We found that the effective linear expansion coefficient and the free-volume fraction are sensitive to annealing, and the secondary working point in vicinity of the Tvs was confirmed by experiment. We confirmed that relative displacement under tensile stress depends strongly upon the state of amorphicity of the sample. We think that applied stress level and the values of the Tvs temperature at each stress level are very useful information for work with consolidated powders.