Soft-magnetic Co-Fe-Nb-B-P high-entropy bulk metallic glasses with enhanced saturation magnetic flux density and superior strength

New soft magnetic Co_40–30Fe_30–40Nb₅B₂₀P₅ high-entropy bulk metallic glasses (HE-BMGs) were developed through a high-entropy composition design strategy, and their thermal stability, glass-forming ability (GFA), along with magnetic and mechanical properties were studied. The results demonstrate that the HE-BMGs exhibit outstanding supercooled liquid stability and high GFA. Notably, a Co₃₅Fe₃₅Nb₅B₂₀P₅ HE-BMG possesses a large supercooled liquid region (ΔT_x) of 66 K and a critical diameter for glass formation (d_c) of 2.0 mm. Compared to a Co₇₀Nb₅B₂₅ counterpart, the Co₃₅Fe₃₅Nb₅B₂₀P₅ HE-BMG exhibits distinct sluggish crystallization behavior and higher crystallization activation energy, despite both alloys precipitating a similar complex Fe₂₃B₆-type phase during initial crystallization. The HE-BMGs also exhibit excellent soft magnetic and mechanical properties with saturation magnetic flux density, coercivity, effective permeability at 100 kHz, yielding strength, and compressive plastic strain of 0.93–1.02 T, 2.9–6.7 A/m, 7000–7700, 4091–4163 MPa, and 0.3–1.0 %, respectively. The combination of high GFA, large ΔT_x, and superior soft magnetic and mechanical properties highlights their potential as advanced functional and engineering materials.