Achieving high strength and ductility in a 3D-printed high entropy alloy by cooperative planar slipping and stacking fault

3D printing is increasingly becoming prevalent for the fabrication of high entropy alloys (HEAs) due to the unrivaled design freedom and net-formability. However, most 3D-printed HEAs suffer from poor printability and printing defects, displaying unsatisfactory mechanical properties for structural applications. This work reveals the near-fully dense (FeCoNi)86Al7Ti7 HEA with complex geometry and superior mechanical properties prepared by selective laser melting (SLM). During the SLM process, the rapid solidification rate induces a hierarchical structure consisting of columnar grains, cellular substructure, and L21-phase nanoprecipitates along cellular boundaries. This SLMed (FeCoNi)86Al7Ti7 HEA displays excellent mechanical properties with an ultimate tensile strength of 1090 MPa and a tensile elongation of ∼30%. The microstructure analysis reveals that the cooperative planar dislocation slipping and stacking faults contribute to the stable strain hardening ability and sustained deformation of (FeCoNi)86Al7Ti7 HEA.