Unveiling the unique bifunctionality of L12-structured nanoprecipitates in a FeCoNiAlTi-type high-entropy alloy

Nanoprecipitation strengthening has been widely adopted as an effective way to design high-strength alloys, which generally leads to the loss of ductility. Here we unveil the unique bifunctionality of L12-structured nanoprecipitates in a FeCoNiAlTi-type high entropy alloy , enabling the combined increase of tensile strength and ductility. Results show that as-quenched precipitate-free matrix alloys undergo thermally-induced martensite transformation and form the body-centered cubic martensite phase with limited tensile ductility. In strong contrast, when introducing the dense coherent L12-type nanoprecipitates, the face-centered cubic matrix is temporarily stabilized, which in turn promotes the microbands-induced plasticity associated with stress-induced martensite transformation upon deformation. This allows us to achieve significantly improved work hardening capability and excellent plastic deformation stability at a high-strength level. These new findings reshape our understanding of the precipitation strengthening and could provide useful guidance for developing highperformance alloys by regulating the coherent nanoprecipitate and martensitic phase transformation.

Automated summary

The unique bifunctionality of L12-structured nanoprecipitates in a FeCoNiAlTi high entropy alloy is unveiled, which allows for an increase in tensile strength and ductility. The introduction of dense coherent L12-type nanoprecipitates stabilizes the face-centered cubic matrix, promoting microbands-induced plasticity associated with stress-induced martensite transformation. This leads to significantly improved work hardening capability and excellent plastic deformation stability at a high-strength level.