Brittle interfacial layer suppression in Cf/C brazed joints with refractory metal via hierarchical microstructure engineering

Abstract Brazing carbon fiber reinforced carbon matrix composites (C f /C) to metals remains a core technological challenge in manufacturing high-temperature composite components for aerospace applications. Although traditional active brazing filler metals can achieve good wetting of the composites, uncontrolled interfacial reactions on the C f /C side lead to the formation of continuous brittle phases, and large residual stress undermine the reliability of the joint. In this study, a self-prepared face-centered cubic (FCC) FeCoNiAlCuTi high-entropy alloy was used as the brazing filler metal. The aim was to exploit its high mixing entropy to suppress the formation of a continuous brittle phase at the C f /C interface. Experimental results showed that the brazed seam forms a multi-layered structure, mainly composed of the C f /C side reaction zone, the Nb solid solution banded zone, and the eutectic zone. No continuous brittle layer formed at the C f /C side interface, and a gully-shaped interlocking interface was formed with the FeCoNiAl ductile phase. This strategy transfers part of the joint stress to the internal FCC phase. Finite element simulations indicated that the peak Mises stress was reduced from 371 MPa to 274 MPa. Under the optimal brazing parameters of 1340 ℃ for 20 min, the shear strength of the joint reaches 40.7 MPa. Briefly stated, this study alleviated the initiation and growth of brittle reactive layers at the interface of C f /C composites, providing important support for the development of high-performance bonding processes for C f /C composites and facilitating their practical application in high-temperature aerospace components.