Increasing fatigue resistance in ordered intermetallic alloys with multi-element symbiosis

Intermetallic alloys, recognized for the long-range atomic ordering and resultant impressive mechanical properties, are highly sought after in various advanced fields, including aerospace, automotive, and nuclear energy. However, their widespread application is still hindered seriously due to the poor fatigue endurance. Here, we design a new-type L12-structured multi-element symbiotic intermetallic alloy (MSIMA) and achieve a fatigue limit of ~1,100 MPa that remarkably surpasses its yield strength by 1.1 times, which is superior to other structural alloys currently in use. The complex sublattice occupation strengthens the alloy by increasing the antiphase boundary energy of the superlattice, thereby suppressing the fatigue-induced lattice defects. Concurrently, the multi-element symbiosis enables the modulation of local chemistries and the architecting of the disordered interfacial nanolayer (DINL) near grain boundaries, thereby shifting the fatigue fracture mode from intergranular to transgranular cracking. Furthermore, serving as the ductilizing sources, these DINLs facilitate the unusual anti-fatigue mechanisms—mechanical faulting and twinning—that are rarely observed in ordered alloys at room temperature. This deformation behavior effectively alleviates the strain localization and blunts the crack propagation, thereby enhancing their fatigue resistance. Leveraging multi-element symbiosis, protective interfacial nanolayers are engineered in an intermetallic alloy. This results in a high fatigue limit of ~1,100 MPa, far exceeding that of conventional intermetallic alloys.