As functional metal materials, immiscible alloys demonstrate wide application prospects in industrial and electronic fields. Immiscible alloys with a uniformly distributed minority phase are a potential substitute for the materials applied in the manufacture of electric contactors and wear-resistant automotive components. Understanding the evolution of various microstructures of immiscible alloys and its correlation with their wear behavior is crucial for their industrial applications. Owing to the liquid-phase separation characteristics of binary Cu-Co and ternary Cu-Co-Fe immiscible alloys, segregation occurred or even a layered microstructure was formed by using conventional casting methods, and obtaining a uniform microstructure was difficult, which seriously limited their applications. This study presents a new strategy for inhibiting the liquid-phase separation and improving the properties of immiscible alloys. Under a high magnetic field, the microstructure of an undercooled alloy was changed, affecting its wear behavior. The experimental results reveal that the microstructures of Cu₅₀Co₅₀ and Cu₅₂Co₂₄Fe₂₄ alloys showed dendritic morphology at modest undercooling without a magnetic field, while the microstructure of Cu₅₀Co₅₀ alloy exhibited a core-shell structure and Cu₅₂Co₂₄Fe₂₄ alloy exhibited an eccentric core-shell structure under large undercooling. Moreover, the application of a high magnetic field resulted in the more uniform microstructure of Cu₅₂Co₂₄Fe₂₄ alloy. With the application of a high magnetic field, the second phases generated by the phase separation of Cu₅₀Co₅₀ and Cu₅₂Co₂₄Fe₂₄ alloys were elongated parallel to the magnetic field direction, and the size of second phases in the alloys decreased significantly in the perpendicular field direction, however, the microstructures of the Cu₅₂Co₂₄Fe₂₄ alloy showed a more uniform distribution. Specimens with large undercoolings in Cu₅₀Co₅₀ and Cu₅₂Co₂₄Fe₂₄ alloys exhibited excellent wear resistance regardless of the application of a high magnetic field. Any alloy that examined abrasive and adhesive wear mechanisms during the wear tests was characterized by rough surfaces generated by material detachment and parallel scratches in the sliding direction. Furthermore, the Cu₅₂Co₂₄Fe₂₄ alloy has a high hardness and a relatively uniform distribution of microstructure under a magnetic field, resulting in the best wear resistance.