Manipulating internal flow units toward favorable plasticity in Zr-based bulk-metallic glasses by hydrogenation

This work intends to manipulate the internal flow units in Zr55Cu30Ni5Al10 bulk-metallic glasses (BMGs) through plasma-assisted hydrogenation to generate a positive microalloying effect on plasticity. Based on the cooperative shear model theory, serration-flow statistics during nanoindentation loading and creep tests during the holding stage were used to analyze the influence of hydrogen on the behavior of flow units in BMGs. Experimental observations showed that the hydrogen in the Zr55Cu30Ni5Al10 BMGs caused mechanical softening, plasticity improvement, and structural relaxation. Analysis also showed that the average volume, size, and activation energy of internal flow units in the BMGs all increased as a result of the increase in the hydrogen content. The hydrogenation in the BMGs was found to lead to a proliferation of shear bands, which promoted plasticity. The aggregation of these internal flow units reduced the stress required for plastic deformation through shear bands, ultimately causing softening and structural relaxation.