Achieving high strength and toughness in microlaminated duplex medium entropy alloys via dual B2 nanoprecipitates

Heterogeneously laminated duplex structures offer a promising approach to overcoming the strength–ductility trade-off in alloys. However, this often comes at the expense of fracture toughness—particularly at gigapascal-level yield strengths—due to strain incompatibilities at interfaces. In this work, we develop a Fe-based medium entropy alloy (Fe-MEA) featuring ordered body-centered cubic (B2) nanoprecipitates embedded within laminated face-centered cubic (FCC) and body-centered cubic (BCC) phases. These engineered interfaces act as prolific, stable, and long-lasting dislocation sources, substantially improving toughness, while simultaneously serving as strong dislocation barriers to enhance strength. The dual-nanoprecipitate-reinforced Fe-MEA demonstrates an exceptional combination of properties: a yield strength of ∼1350 MPa, ductility of ∼18 %, and fracture toughness of ∼166 MPa·m^0.5. Dynamic grain refinement and crack branching further contribute to enhanced energy absorption. Although showcased in Fe-MEAs, this structural design strategy offers a promising pathway for developing other strong and ductile alloys— such as complex multi-element alloys—with superior fracture resistance.