Work-hardening and susceptibility to plastic flow in metallic glasses (rolling deformation)

Fe-Ni-base metallic glass ribbons were rolled “directly” and “indirectly” by changing the rolling direction with respect to the ribbon axis. In the case of direct rolling, no visible deformation bands appeared on the rolling surfaces (except at the edges) but wavy deformation markings appeared on the side surfaces. In the case of indirect rolling, however, the deformation markings developed on the entire surface; they were wavy and straight in appearance on the rolling and side surfaces, respectively. Tensile tests, performed on the samples rolled directly and indirectly show little and much change in fracture stresses, respectively. As a result of the intersecting of plastic flow systems, fracture shear stresses increase by 7% compared with those of as-quenched samples. Fracture shear stresses on a predeformed area were, however, found to be 3% lower than those for an undeformed area. These results are discussed in terms of both work-hardening and work-softening in metallic glasses.