Additive manufacturing of cryogenic chemically complex alloys with sponge bone-like reticular nanoscale superstructure

The mechanical properties of most engineering materials degrade at low temperatures due to increased resistance to dislocation movement in the lattice, hindering stress dissipation via plastic deformation. Consequently, materials are more prone to brittle fracture in stress-concentrated regions rather than exhibiting plastic deformation as seen at room temperature. Herein, we prepared a cryogenic chemically complex alloy (CCA) with a sponge bone-like reticular nanoscale superstructure consisting of L1₂-ordered FCC nanoprecipitates, L2₁-ordered BCC nanoprecipitates, and high-density dislocations via powder bed fusion (PBF) and subsequent aging treatment. The results reveal that appropriate aging induces the formation of a unique nanoscale superstructure, enhancing both structural stability and strength regulation. Microstructural characterization shows the precipitation of coherent L1₂ and incoherent L2₁ nanoprecipitates, which significantly impede dislocation motion and contribute to precipitation strengthening. Among the tested conditions, the sample aged for 2 h exhibits the most balanced mechanical properties, with a yield strength of 1130 MPa, ultimate tensile strength of 1492 MPa, and elongation of 18 % at room temperature. At 77 K, the yield strength and UTS further increase to 1331 MPa and 1786 MPa, respectively, while maintaining a comparable elongation of 17.7 %. Mechanism analysis indicates that deformation at room temperature is dominated by dislocation glide, while at cryogenic temperature, a combination of dislocation–precipitate interactions and nanotwin formation enhances the strength–ductility synergy. Quantitative analysis suggests that L1₂ precipitation contributes approximately 447 MPa to the total strength, accounting for ∼40 % of the strengthening effect. These findings provide valuable insights into microstructure–property relationships in HEAs and offer a promising route toward designing high-performance materials for extreme service environments via additive manufacturing.