Enhanced fatigue endurance limit of Cu through low-angle dislocation boundary

How to remarkably elevate the high-cycle fatigue resistance of metallic materials under cyclic loading is a crucial, yet technically challenging issue for major structural applications. Either traditional strengthening approaches or newly-developed hierarchical nanostructural modifications has been demonstrated to usually display a limited ability of enhancing the 10 ⁷ -cycle fatigue endurance limit. Here, we introduce massive nano-scaled low-angle dislocation boundaries in coarse grained pure Cu by means of simple drawing process, not only enhancing the tensile strength obviously, but also imparting a fatigue limit as high as 130 MPa and a fatigue ratio of 0.35, which is a record for pure Cu. Upon cyclic loading, the extensive activation of strongly confined dislocation slip within homogeneous dislocation cells (with cell size of about 300 nm) effectively mediates cyclic plastic strain with slightly cyclic softening. The elevated stress resistance of DC Cu to cyclic loading is primarily attributed to the high density of built-in low-angle dislocation cells, which are strong and also suppress local surface roughening and crack initiation, thereby contributing to an enhanced fatigue life.