Extraordinary strength-ductility synergy in chemically complex intermetallic alloys with hierarchical dual-phase nanostructures

Developing structural materials with an excellent combination of strength and ductility is a parament task in advanced industries. Conventional intermetallic alloys (IMAs) usually suffer from insufficient ductility, which severely restricts their practical applications. In this study, we developed a novel high-performance bulk chemically complex intermetallic alloys (CCIMAs) in the multicomponent (Ni, Co)₃(Si, Ti, Al) system. The microstructure, mechanical properties, and associated deformation behaviors were systematically investigated through combinational analyses such as three-dimensional atom probe tomography (3D-APT) and transmission electron microscope (TEM). By multi-step cold rolling and annealing path, the newly developed (Ni, Co)₃(Si, Ti, Al)-type alloys show a unique hierarchical dual-phase nanostructure, exhibiting extraordinary strength and ductility at ambient temperature. The yield strength, tensile strength, and ductility can reach ∼1011 MPa, ∼1690 MPa, and 35 %, respectively. Detailed TEM and 3D-APT analyses revealed that the coherent Co-rich disordered nanoparticles precipitated out from the L1₂ matrix region. These reversely precipitated nanoparticles are mainly sheared by superlattice dislocation pairs and generate a significant strengthening effect. Superlattice stacking faults (SSFs) were also observed at large deformation due to the reduction of stacking fault energy and high stress level that reaches a critical value. These findings are expected to accelerate the innovative design of ultra-strong yet ductile intermetallic compounds for structural applications.