Achieving extreme rejuvenation and strain-hardening of metallic glass

Rejuvenation has been demonstrated as a viable method to enhance plasticity and strain-hardening in metallic glasses (MGs). In this study, a substantial rejuvenation of MG is accomplished through the implementation of the triaxial compression-torsion technique of indentation-notched MGs, leading to a notable enhancement in their plasticity and strain-hardening. In comparison to cast and cut notched MGs, the rejuvenated MG prepared using indentation-notched MGs exhibits necking phenomenon during the tensile process as opposed to the conventional shear band (SB) damage mode. Hydrostatic compressive stress is instrumental in regulating the degree of rejuvenation, and high hydrostatic stress serves as the primary catalyst for rejuvenation. It is confirmed that the rejuvenation treatment result in a decrease in the proportion of short-range ordered (SRO) and medium-range ordered (MRO) structures, as well as a decrease in polyhedron content within the MG. In the region of large plastic deformation, the icosahedral structure is destroyed. Furthermore, the studied results also imply a decline in the proportion of 2-atom and 3-atom polyhedron connection modes, accompanied by an increase in the proportion of 1-atom and 4-atom polyhedron connection modes. In addition, the density and nano-hardness of rejuvenated MGs are found to be lower in comparison with cast MGs. This decline is attributed to the increase in free volume during rejuvenation, particularly in the region of high plastic deformation. This study elucidates the rejuvenation mechanism of MGs under large plastic deformation and develops an effective rejuvenation method to enhance the plasticity and strain-hardening of MGs. These findings offer novel perspectives for optimizing the properties of MGs and provide a scientific basis for future material design and processing.