Planar Flow Casting of Fe‐Based Amorphous Ribbons: Puddle Evolution and Ribbon Formation

Planar flow casting (PFC), owing to its high cooling rate, offers significant potential for fabricating magnetic materials such as high‐silicon steels and Fe‐based amorphous ribbons. Herein, a 2D transient volume‐of‐fluid‐based coupled flow and heat‐transfer model is developed to investigate the PFC process of Fe‐based amorphous ribbons. The simulations reveal the evolution of the puddle and gas entrainment, as well as their effects on the thermal field, flow dynamics, air‐pocket formation, and ribbon morphology. Gas entrainment occurs predominantly during the spreading stage, where the entrapped air pockets hinder heat transfer at the melt–roller interface, trigger interfacial instabilities, and deteriorate ribbon surface quality and magnetic performance. Roller speed plays a decisive role: low speeds favor longer puddle stability, whereas high‐speeds intensify interfacial fluctuations and gas entrainment, leading to reduced stability but thinner ribbons with higher cooling rates. Excessively high roller speeds, however, cause thermal accumulation on the roller surface, impairing process stability and compromising the functional properties of the ribbons and derived soft magnetic materials.