Plastically deformed MGs develop inhomogeneity and show harder and softer regions [16]. While this could in principle be associated with a BE according to the composite model, a MG provides no basis for a dislocation-based theory. The search for a BE in plastic flow is hindered by the softening of MGs associated with shear-banding (in contrast to the work-hardening familiar in conventional alloys). Anelastic deformation is, however, of interest as its time-dependence must relate to relaxation processes in the MG structure that in turn should be connected to the onset of plasticity. In particular, anelasticity may offer a way to study the operation of the shear transformation zones (STZs [17]) often used to interpret the deformation of MGs. Fujita et al. have used torsion tests to observe anelasticity in MGs loaded (at maximum, on the cylindrical sample surface) to 30%, 16% and just 4% of the shear yield stress τy [18]. In the present work we apply torsion to MG samples to reach stresses up to 24% of τy, and for the first time in the elastic regime investigate the effects of torque reversal.
