ACOUSTIC-EMISSION DURING HETEROGENEOUS AND HOMOGENEOUS PLASTIC-FLOW OF A METALLIC-GLASS

Measurements have been made of the acoustic emission that occurs durin g the plastic deformation of metallic glass subjected to various heat treatments. It is shown that for the same temperature and deformation rate it is possible to have either homogeneous flow with no acoustic e mission or localized flow accompanied by intense discrete acoustic emi ssion, depending on the preliminary annealing conditions. From an anal ysis of the experimental results, it is deduced that the nature of the plastic flow of metallic glasses is determined by the structural rela xation rate at the experimental temperature and the conditions of inte nse structural relaxation, that plastic flow is homogeneous viscoelast ic, and, under the conditions of kinetically inhibited structural rela xation, that it is localized and occurs by a dislocation-like mechanis m. (C) 1997 American Institute of Physics.