Effects of Co, Fe Alloying on the Microstructures and Mechanical Properties of Ni–Co–Fe–Al–Ti–B Complex Component Intermetallic Alloys

Based on metastable engineering and valence electron concentration design, three (Ni 12– x – y Co x Fe y Al 2 Ti 2 ) 97.5 B 2.5 ( x = 4, y = 2; x = 3.5, y = 1.5; x = 3, y = 1) complex component intermetallic alloys (CCIMAs) are prepared by adjusting Co and Fe contents. Through multiscale characterization and mechanical testing, the effects of Co/Fe alloying degree on microstructural evolution, solidification path, and mechanical behavior are systematically investigated. The results show that the synergistic addition of Co/Fe shifts the eutectic point toward the Ni‐rich side, significantly expanding the formation range of the B2 phase. This promotes the precipitation of B2 primary dendrites, with its volume fraction and size increasing notably as the alloying degree rises. Mechanical tests indicate that the hardness and compressive yield strength of the alloys improve with the addition of Co/Fe. The optimized composition (Ni 7 Co 3.5 Fe 1.5 Al 2 Ti 2 ) 97.5 B 2.5 exhibits a compressive yield strength of 1066 MPa and a fracture strain of 53% while retaining ≈450 MPa yield strength at 950 °C. This work elucidates the mechanism by which Co/Fe alloying regulates the dual‐phase microstructure by altering the eutectic reaction pathway, thereby achieving performance optimization. It provides guidance for designing novel high‐performance CCIMAs, facilitating the attainment of desired microstructures and improved performance.