Improving the plasticity of transition-metal-based high-entropy bulk metallic glasses via Ag-induced phase separation

High-entropy bulk metallic glasses (HE-BMGs) exhibit unique combinations of mechanical and magnetic properties due to their complex compositions. This study investigates the effects of minor Ag additions on the glass-forming ability (GFA), thermal stability, and mechanical behavior of [Fe_0.25Co_0.25Ni_0.25(Si_0.3B_0.7)_0.25]_100-xAg_x (x = 0, 0.1, 0.3, 0.5 at.%) HE-BMGs. Results indicate that Ag promotes phase separation, introducing nanoscale heterogeneity, which enhances plasticity and mechanical performance. Optimal Ag content (0.3 at.%) achieved an 15.7 % plastic strain and 3875 MPa yield strength, attributed to the formation of short-range ordered structures and shear transformation zones. These nanoscale heterogeneities acted as pinning sites, facilitating shear-band branching and stable deformation. Excessive Ag content, however, induced brittle phase formation and structural stress, reducing plasticity. Furthermore, the saturation magnetization peaked at 0.84 T with minimal degradation of GFA. These findings highlight the potential of controlled phase separation in designing HE-BMGs with superior strength-ductility synergy for advanced structural applications.