Localized and homogeneous plastic flow in bulk glassy Pd40Cu30Ni10P20: An acoustic emission study

A detailed study of plastic flow of bulk glassy Pd40Cu30Ni10P20 has been performed using an acoustic emission (AE) technique from room temperature up to the low-temperature end of the supercooled liquid region. The AE measurements allowed for clear identification of both inhomogeneous (slip-band mediated) and homogeneous plastic flow modes as well as the transition between these. It is argued that inhomogeneous flow occurs when structural relaxation-induced homogeneous deformation is incapable of accommodating plastic strain in a metallic glass at a rate imposed externally. Within this framework, the boundary between the flow modes as a function of temperature and strain rate is calculated and verified to be very close to experimental observations. The results of AE measurements witness that the dynamic properties of AE sources-shear bands-are essentially the same at different temperatures, i.e., the temperature affects the number of slip bands but does not affect their velocity or dimensions. (C) 2013 AIP Publishing LLC.