KINETICS OF ISOTHERMAL CREEP IN METALLIC GLASSES INCLUDING THE STATISTICAL DISTRIBUTION OF ACTIVATION PARAMETERS

A generalized theoretical model is proposed fur tile structural relaxa tion of metallic glasses under load. Structural relaxation is treated as a set of irreversible, uncorrelated, two-stage atomic displacements in some regions of the structure, the ''relaxation centers.'' In load ed samples structural relaxation acquires a directional character lead ing to the buildup of plastic deformation in accordance with the magni tude and orientation of the applied mechanical stress. General equatio ns are obtained for creep kinetics including a continuous statistical distribution of the principal activation parameters. These equations a re compared with the results of a special experiment. The model is fou nd to provide an adequate interpretation of the observed creep kinetic s, except or the first 10(1)-10(2) seconds after loading. It is argued that the initial stage of creep is determined by reversible atomic re alignments in relaxation centers having symmetric two-well potential. (C) 1997 American Institute of Physics.