High strength Al0.7 CoCrFeNi2.4 hypereutectic high entropy alloy fabricated by laser powder bed fusion via triple-nanoprecipitation

Eutectic high-entropy alloys, composed of FCC/B2 phases with a narrow solidification interval and excellent fluidity, have become a new hotspot in additive manufacturing. Nevertheless, their microstructures exhibit significant sensitivity to processing parameters, feedstocks, and composition, ultimately limiting the alloys' engineering applications. Here, a hypereutectic Al0.7 CoCrFeNi2.4 alloy with a low cracking susceptibility index was designed by Thermo-Calc calculation and fabricated by laser powder bed fusion. Results show that the as-printed Al0.7 CoCrFeNi2.4 alloy manifests a stable cellular structure, coupled with appreciable ultimate tensile strength ( >= 1200 MPa) and ductility ( >= 20%) over a wide range of processing parameters. After aging at 800 degrees C for 30 min, outstanding strength (1500 MPa) and elongation (15%) were obtained. Considerable mechanical properties after aging stem from a triple strengthening mechanism, i.e., L12 nanoprecipitates and rod-shaped B2 particles within the FCC matrix, along with Cr-enriched spherical nanoparticles in the B2 phase. Meanwhile, hierarchical structure, i.e., FCC dominated matrix, a discontinuous B2 phase, a precipitation-free zone in the B2 phase, and a K-S orientation relationship between FCC and B2, facilitate to maintain excellent plasticity. These results guide designing HEAs by AM with controllable microstructures and outstanding mechanical properties for industrial applications. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.