Microstructural evolution and magnetic property of a rapidly solidified ternary Fe_37.5Cu_37.5Sn₂₅ peritectic-type alloy

The liquid Fe_37.5Cu_37.5Sn₂₅ peritectic-type alloy was rapidly solidified by glass fluxing, drop tube, and melt spinning techniques. The solidification structures consisted of three phases, including the αFe solid solution and the Cu₃Sn and Cu₆Sn₅ intermetallic compounds under different conditions. In this work, the bulk undercoding ΔT equals the liquidus temperature T_L minus the nucleation temperature T_N of the primary solid phase. During the bulk undercooling process, a maximum liquid undercooling of 272 K (0.18T_L) was achieved. Metastable liquid phase separation was induced if the undercooling exceeded 177 K. Within a moderate undercooling range from 8 to 177 K, the solidified structures showed coarse dendrites, and the dendritic growth velocity increased to 41.5 mm/s following a power relation. As the drop tube technique provided a containerless state, a maximum surface cooling rate of 3.5 × 10⁴ K/s was achieved. The alloy droplets displayed metastable liquid phase separation even at the largest droplet diameter of 944 μm. The cooling rate and thermal Marangoni migration were found to greatly influence the phase-separated patterns of the alloy droplets. Under the melt spinning condition, the microstructures of the Fe_37.5Cu_37.5Sn₂₅ alloy ribbons were significantly refined and displayed soft magnetic characteristics. Furthermore, the experimental results demonstrated that the grain size of the αFe phase affected the coercivity of the alloy ribbons.