Abstract: The newly emerged chemically complex intermetallic alloys (CCIMAs) are expected to achieve breakthrough advancements in metallic materials. However, many existing CCIMAs still suffer from limited yield strength due to the single-phase structure, seriously limiting their widespread applications. Here, we successfully resolve this critical issue by controllably introducing the local chemical disorder (LCD) with face-centered-cubic (FCC) structure into the L1₂-type Ni-Co-Si-Ti-Al-based CCIMA, achieving a superior yield strength of ∼1033 MPa and ultimate tensile strength of ∼1730 MPa, and outstanding tensile elongation of ∼29 %. The unique LCD produces an anomalous strengthening effect, which is estimated to be ∼345 MPa. Meanwhile, these disordered nanoparticles with lower stacking fault energy also promote the nucleation of superlattice intrinsic stacking fault (SISF) networks in the CCIMA, contributing to a high strain-hardening rate in the late stage of plastic deformation. This work provides a new insight into developing a strong yet ductile CCIMA for advanced structural applications.

Key words: Chemically complex intermetallic alloys, Ordered matrix superlattice, Local chemical disordering, Mechanical behavior, Deformation mechanism