Ultrastrong and ductile FeNi-based alloys through Pd-containing multicomponent L12-type precipitates

[Display omitted] •Introduces novel FeNi-based alloys strengthened with multicomponent L12-type precipitates containing Palladium (Pd), significantly boosting strength while preserving ductility.•Achieved an eightfold yield strength increase in FeNi-based alloys with novel Pd-containing precipitates, maintaining over 10 % ductility.•Pd addition to L12 precipitates modifies thermodynamic stability, morphology, coherency, and strengthening effects, offering advanced alloy design pathways.•Discovered that Pd incorporation changes precipitate shapes from spherical to acicular, reducing interface mismatch and enhancing material performance.•Demonstrated the dual role of Pd in precipitate nucleation and shear modulus anisotropy elimination, informing new alloy designs. Precipitation strengthening stands as a paramount strategy for enhancing the mechanical properties of FeNi-based alloys. Conventional precipitates used for strengthening typically contain only two major constituent elements selected from Ni, Al, and Ti. However, knowledge about the intrinsic properties and strengthening mechanisms of multicomponent precipitates remains limited. Here, we propose introducing novel multicomponent L12-type precipitates containing palladium (Pd) to strengthen FeNi-based alloys. The strengthened FeNi alloy achieves an eightfold increase in strength compared to the FeNi matrix while maintaining good ductility. Using meticulous micro-characterization and energy-dispersive X-ray spectroscopy (EDS) techniques, in conjunction with first-principles calculations, this study investigated the effects of Pd addition on the thermodynamic stability, morphology, coherency, and strengthening mechanisms of the precipitates. Results indicate that the addition of Pd induces the nucleation of L12-type precipitates, increases their ductility, and eliminates anisotropy in the shear modulus of the precipitates. Excessive Pd content can alter the shape of precipitates from spherical to acicular due to increased interfacial mismatch between the precipitates and the FeNi matrix. These insights shed light on the impact of Pd addition on the intrinsic properties of L12-type precipitates, offering a promising pathway for the design of advanced FeNi-based alloys with optimized mechanical performance.