Mechanisms of plasticity enhancement in FeCoNi-SiB-Cu high-entropy bulk metallic glass via rejuvenation treatments

This study investigates the effect of rejuvenation treatments, namely cryogenic thermal cycling (CTC) and cyclic elastic loading (CEL), on the mechanical properties of [Fe 0.25 Co 0.25 Ni 0.25 (Si 0.3 B 0.7 ) 0.25 ] 99.7 Cu 0.3 high-entropy bulk metallic glass (HE-BMG). The CTC treatment with an upper temperature of 472 K significantly enhances the plasticity, yielding a plastic strain of 20 % and a yield strength of 4500 MPa, due to the formation of increased free volume and short-range ordered structures. Similarly, the CEL treatment at 1300 N improves plastic strain to 16 % with a yield strength of 4200 MPa, resulting from structural heterogeneity and stress distribution modification. However, combining CTC and CEL treatments leads to the growth of hard and brittle Fe(Co, Ni) 23 B 6 phases, causing stress concentrations that reduce plasticity. This work elucidates the mechanisms behind plasticity enhancement and degradation in HE-BMGs and provides a pathway for designing high-strength, high-plasticity metallic glasses through precise structural control at the atomic level.