Nano-Architected Metallic Metamaterial With Enhanced Fatigue Resistance via Dislocation Starvation

Metal single crystals often suffer from severe strain localization under cyclic loading due to the absence of grain boundaries that act as crystallographic obstacles, resulting in their low fatigue resistance despite their advantages in applications requiring microstructural stability. This study demonstrates that this intrinsic trade-off can be overcome by exploiting dislocation starvation that arises as metal single crystals are reduced to the nanoscale. Tension-compression fatigue tests on 300 nm-wide nickel (Ni) single crystals reveal a fatigue-crack initiation limit exceeding 800 MPa, more than an order of magnitude higher than that of bulk Ni single crystals. In situ transmission electron microscopy experiments directly capture dislocation starvation during cyclic loading, confirming that strain localization, which typically serves as a precursor to fatigue-crack initiation, is completely suppressed. Based on this mechanism, a nano-architected Ni single-crystal metamaterial is designed to macroscopically harness dislocation starvation. Despite a relative density of only ∼50%, the metamaterial exhibits a fatigue-crack initiation limit about twice that of homogeneous Ni single crystals. These findings introduce a dislocation-starvation-driven design principle for simultaneously enhancing fatigue resistance and reducing weight in metal single crystals, thereby opening a new paradigm beyond the conventional limitations.