<p>A cost-effective Fe-P-C nanocrystalline alloy (Fe₈₅P₉C₆) was developed via melt-spinning by eliminating expensive alloying elements and post-annealing steps. The microstructure consists of an amorphous matrix with uniformly dispersed nanocrystalline clusters, featuring an average size of approximately 5 nm. This dual-phase structure remains thermally stable up to 569 K and results in excellent magnetic and mechanical performance, including a high saturation magnetic induction of 1.69 T, Vickers hardness of 621 HV, and outstanding bending ductility. Crystallization proceeds via the transformation of a metastable fcc-(Fe,P,C) phase into α-Fe, Fe₃C, and Fe₃P, driven by internal stress arising from atomic size mismatch. Continuous heating and cooling transformation diagrams further reveal that this process can be precisely controlled to optimize phase evolution. The high Fe content and stress-relaxed nanocrystalline clusters contribute to enhanced in-plane magnetic anisotropy and rapid domain response. This simplified, annealing-free approach not only reduces material and processing costs but also provides a viable pathway for scalable fabrication of next-generation soft magnetic alloys with superior performance and manufacturability.</p>