From process to performance: a review on laser additive manufacturing of eutectic high-entropy alloys

Multi-component elemental eutectic high-entropy alloys (EHEAs), exemplified by AlCoCrFeNi2.1, have emerged as promising structural materials due to their unique dual-phase B2/FCC lamellae microstructures and resulting exceptional mechanical properties. However, there are still certain limitations in tailoring the microstructure of EHEAs using conventional methods. Laser additive manufacturing (AM) techniques offer significant opportunities to customize chemical and microstructural heterogeneities across multiple scales, thereby enhancing alloy properties, facilitated by extreme non-equilibrium kinetics. AM effectively refines the eutectic lamellae architecture and enhances interface density, thereby upgrading mechanical properties, service properties, and functional properties, which far surpass those of conventionally processed counterparts. For instance, in the as-built state, laser powder bed-fused AlCoCrFeNi2.1 typically achieves a yield strength of 900–1100 MPa, approximately 30–50% higher than its as-cast counterpart, while also exhibiting superior wear and corrosion resistance. However, previous works are rather scattered across various aspects, including composition, processing, microstructure, and properties, in the AM-ed AlCoCrFeNi2.1 system. This review systematically revisits the effects of alloying, processing strategy, temperature, and post-treatment on the microstructural evolution, deformation behavior, strengthening mechanisms, and various performances of the AM-fabricated EHEA system, establishing the process-structure–property relationships. Furthermore, future research directions are proposed to fully exploit the potential of AM-EHEAs in demanding engineering applications.