Simultaneously Enhanced Strength-Ductility of AlCoCrFeNi _2.1 Eutectic High-Entropy Alloy via Additive Manufacturing

Abstract

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, AlCoCrFeNi_2.1 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.

Keywords: Eutectic high-entropy alloy; Laser metal deposition; Microstructure; Mechanical property