Impact of cryogenic cycling on tracer diffusion in plastically deformed Pd40 Ni40 P20 bulk metallic glass

Hassanpour A.; Vaidya M.; Divinski S.V.; Wilde G.

Abstract

The impact of thermo-mechanical treatment, in particular of room temperature high-pressure torsion (HPT), cold rolling and cryogenic thermo-cycling on shear band diffusion in a model Pd40Ni40P20 bulk metallic glass is investigated. Tracer diffusion measurements reveal the existence of fast short-circuit diffusion in deformed glasses and the diffusion enhancement was found to depend on the processing mode. The HPT processing imposes an extremely large shear deformation under quasi-hydrostatic conditions whereas cold rolling induces individual well-separated shear bands, though shear band diffusion is found to be faster after cold rolling. The cryogenic thermo-cycling enhances the shear band diffusion further and a conceptual explanation for the processes leading to kinetic rejuvenation is proposed.