Continuous Stress Annealing Enables Ultralow‐Loss Fe‐Based Amorphous Alloys With Superior Magnetic Softness for Industrial Manufacturing

ABSTRACT Fe‐based amorphous alloys are attractive soft magnetic materials for next‐generation power electronics, yet simultaneously achieving high saturation magnetic flux density ( B s ), low coercivity ( H c ), and low core loss under scalable processing conditions remains challenging. Here, a composition–stress coupling strategy combining moderate Co substitution with optimized continuous stress annealing (CSA) is proposed to enhance magnetic performance and manufacturability. The optimized Fe 81.5− x Co x Si 3.7 B 14.5 C 0.3 ( x = 1) alloy is designed and exhibits outstanding properties, including low H c of 0.92 A m −1 , high B s of 1.65 T, ultralow core loss ( P 10/50 ) of 0.031 W kg −1 at 1.0 T and 50 Hz, and an effective permeability ( μ e ) of 12,200 at 1 A m −1 and 1 kHz. Compared with commercial Metglas 2605SA1, H c and P 10/50 are reduced by 46% and 40%, respectively, whereas B s is enhanced. Multiscale experiments and micromagnetic simulations reveal that optimal Co content and CSA induce medium‐range atomic ordering and magnetoelastic coupling, generating robust uniaxial magnetic anisotropy and coherent three‐dimensional magnetization. The CSA process offers a controllable, uniform, and energy‐efficient route suitable for large‐scale industrial production.