7. Bend Stress Relaxation of Amorphous Metallic Alloys Under Isothermal and Nonisothermal Heating Conditions

A model analysis about the relation between the viscosity and the relaxation of bend stresses of ribbonlike amorphous metallic alloys, both under isothermal and nonisothermal conditions, is presented. Additionally, an experimental proof of the theoretical considerations based on the free volume model (FVM) is given. The experimental proof upon a study of the nonisothermal viscous flow behavior of Fe₄₀Ni₄₀Si₆B₁₄ amorphous metallic glass, in the high temperature range around its glass transition temperature, is performed. Additionally a study of the (nonisothermal and isothermal) relaxation of bend stresses in the same ribbonlike alloy at considerably lower temperatures is carried out. It is shown that the FVM interpretation of the two kinds of experimental data is possible with practically one and the same common set of FVM parameters. A new method for quantitative experimental separation of viscous flow caused plastic and anelastic deformations, respectively, is developed. It is shown that the relaxation of the anelastic deformation can be very well described by the empirical equation of Kohlrausch–Williams–Watts.