Achieving high fatigue strength of large-scale ultrafine-grained copper fabricated by friction stir additive manufacturing

The preparation of large-scale bulk materials and the limitation of fatigue strength improvement are two crucial obstacles restricting the industrial applications of ultrafine-grained (UFG) materials. In this study, we success-fully fabricated the large-scale UFG pure copper by using the water-cooling assisted friction stir additive manufacturing (FSAM) method and investigated its high cycle fatigue (HCF) properties. The microstructural characteristics before and after fatigue were almost the same, proving the high microstructure stability of FSAM Cu during the HCF deformation. Therefore, the fatigue strength of FSAM Cu was as high as 130 MPa, and the fatigue ratio (0.30) reached the same level as coarse-grained Cu. This study can provide an efficient method to fabricate large-scale bulk materials with high fatigue resistance, bringing possibility to the engineering appli-cation of UFG materials.