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

The viscous-flow behavior of amorphous Co69Fe4.5Nb1.5Si10B15 alloys has bee n investigated. Thermomechanical analysis experiments showed effective visc osity decreasing monotonically with increasing temperature until steady-sta te viscous-how temperature (T-vs), where the effective viscosity of the rib bon sample showed a minimum but increased after passing through that point. Annealing-induced changes of the free-volume fraction decreased with incre asing 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 T-vs was confirmed by experiment. We conf irmed 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 T-vs temperature at each stress level are very usefu l information for work with consolidated powders. (C) 2001 Elsevier Science B.V. All rights reserved.