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

Abstract

This study investigates the effect of rejuvenation treatments, namely cryogenic thermal cycling (CTC) and cyclic elastic loading (CEL), on the mechanical properties of [Fe_0.25Co_0.25Ni_0.25(Si_0.3B_0.7)_0.25]_99.7Cu_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)₂₃B₆ 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.