Stress relaxation in amorphous alloys

Abstract

The anelastic stress relaxation was measured as a function of time and temperature for amorphous Fe 40Ni 40P 14B 6. An initial fast relaxation occurred which was not resolvable, followed by a slower, first-order rate process with an activation energy of 0.5 eV. It is suggested that this activation energy is controlled by hole migration. Anelastic stress relaxation was also measured after heating for 2 h at 225 °C for a number of amorphous alloys series: Fe x Ni 80− x P 14B 6, Fe x Ni 80− x B 20, Fe x Ni 80− x P 14C 6, Fe 40Ni 40B 20− x P x , Fe 80B 20− x Si x , Fe 85B 15− x Si x , Fe 85− x P 15B x , Fe 85− x P 15Al x , Fe 85− x P 15Si x , Fe 85− x B 15Si x , Fe 85− x B 15P x and Fe 100− x B x . Glass temperatures of some of these series were measured and some obtained from the literature. In all cases the stress relaxation rate increased with decrease in T g. This relation cannot be explained by the free volume quenched in at T g, but can be explained by the change in the structure during the relaxation in the secondary cooling period below T g, or by the change in viscosity of the solid with temperature below T g. The stress relaxation rate was found to increase with increase in the temperature of the melt, followed by a decrease. This increase was interpreted as showing the retention of the increasingly disordered structure of the liquid with increasing temperature. Increasing the contact time of the ribbon with the wheel, which increases the secondary cooling, also increased the stress relaxation rate. This is consistent with the effect of the structure relaxation, during the secondary cooling time, on the stress relaxation rate. Decreasing the ribbon thickness increased the ribbon relaxation rate, consistent with the view that a more disordered structure was initially quenched in.