High-Entropy Alloy Interlayers Toward Advanced Joining for High-Performance Structural Applications: Current Progress and Emerging Challenges

Reliable joining of nickel-based superalloys, composites, or other dissimilar materials combinations remains a persistent challenge in aerospace and nuclear energy applications, where brittle intermetallic compound (IMC) formation, residual interfacial defects, and insufficient service performance restrict the practical deployment. This review systematically examines high-entropy alloy (HEA) interlayers as a promising solution to these challenges. From a compositional perspective, this review discusses the evolution from single-phase solid-solution HEAs to dual-phase, eutectic, and refractory systems. It highlights how their sluggish diffusion kinetics and high phase stability suppress undesired IMC formation and promote sound metallurgical bonding. In terms of structural design, the transition from single-layer to double-layer and sandwich/composite configurations is discussed, demonstrating how these architectures accommodate thermomechanical mismatch and reduce interfacial defects. However, achieving superior joint performance under extreme service conditions requires a synergistic compositional and structural design strategy. Building on these design principles, the novel multiinterlayer composite bonding (MICB) strategy employing a BNi-2/HEA/BNi-2 sandwich interlayer is innovatively developed. Incorporating a core of L1₂-strengthened HEAs or chemically complex intermetallic alloys (CCIMAs), this approach effectively addresses the long-standing strength–ductility trade-off in superalloy joints. Finally, future challenges are also outlined, including the artificial intelligence (AI)-assisted compositional design, high-precision manufacturing methods, and comprehensive performance evaluations. © 2026 The Author(s). Advanced Engineering Materials published by Wiley-VCH GmbH.