Elastic properties and structural relaxation of amorphous Co-P and Fe-P alloys

Abstract

The shear modulus G and Young's modulus E of electrodeposited amorphous Co-P and Fe-P tubes and the corresponding ultrasonic attenuation were measured between 0.1 and 10 MHz by a resonance technique. The accuracy was sufficient to evaluate the bulk modulus K and the Poisson ratio nu from G and E. The effect of structural relaxation on the elastic constants was investigated during continuous heating and several isothermal annealing programs. The quantitative analysis of the results is restrained because of the superposition of reversible and irreversible relaxation processes and because of the nearly unknown pre-annealing effects during the heating periods before isothermal treatment starts. But it is possible to derive some ideas concerning short-range order and structural relaxation from the different behaviour of the elastic moduli and the attenuation as functions of time. Relaxation is described mainly by a homogenisation of the material with respect to excess free volume. There are striking differences between the properties of the two alloy systems, particularly in the effects of structural relaxation on their elastic moduli and on their attenuation of sound, pointing to different short-range orders.