In situ nano-oxides and magnetic field engineering enable exceptional strength-ductility synergy in additively manufactured AlCoCrFeNi2.1 eutectic high-entropy alloys

Abstract

Eutectic high-entropy alloys (EHEAs), exemplified by AlCoCrFeNi_2.1, offer a promising pathway for developing alloys with exceptional strength–ductility synergy due to their unique microstructural features and deformation mechanisms. Building on these characteristics, this study proposes a strengthening and toughening strategy for additively manufactured AlCoCrFeNi_2.1 EHEA by integrating in situ nanometer-scale oxides with the assistance of a magnetic field. The results indicate that the application of a magnetic field refines the columnar grain width (reducing it by 44.9 %), weakens the texture intensity, but increases the dislocation density of the alloy. The external magnetic field does not alter the types of microstructures (FCC/L1₂ phase, BCC/B₂ phase, and nanometer-scale oxides); however, it refines the lamellar spacing, eliminates non-lamellar regions, and increases the volume fractions of the BCC/B₂ phase and nanometer-scale oxides. These microstructural evolutions activate multiple strengthening and toughening mechanisms. Consequently, the application of an external magnetic field enhances both the tensile strength and elongation, reaching 1591 MPa and 23.5 %, respectively, thereby achieving an outstanding strength–ductility synergy.