Simultaneously Enhanced Strength-Ductility of AlCoCrFeNi 2.1 Eutectic High-Entropy Alloy via Additive Manufacturing

The negative effects of thermal cycles in the process of additive manufacture present a challenge for the control of microstructure so as to fabricate the products with improved properties compared to cast. In this work, AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) was prepared by laser metal deposition (LMD). Comparison with the cast samples, the LMD-fabricated EHEA showed significantly enhanced tensile strength (by 19.7%) and increased tensile ductility (by 56.4%). Such enhancement in mechanical properties owing to the refinement of the uniformly distributed eutectic-structure, which was composed of a ductile FCC(L12) phase and a strong BCC(B2) phase embedded with a high density of nano-precipitates. These nano-precipitates effectively pinned the dislocations, resulting strain hardening/dislocation accumulation capability. The present work provides a new strategy to utilize both the high cooling rates of LMD and the eutectic-structure characteristics for achieving homogeneous structures and superior mechanical properties to those prepared by traditional processing techniques.