Plastic Deformation Mechanisms Regulated by Twin Boundary Spacing in Inverse Gradient Nanotwinned Copper

In recent years, gradient nanotwinned copper, which features dual gradients in twin boundary spacing (TBS) and grain size (GS), has become a focal point of research in the materials science field. This structure has been proven to be an excellent nanotwinned system with a highly controllable microstructural gradient. In this study, a new inverse gradient nanotwinned (IGNT) copper structure model is constructed, where TBS and GS exhibit opposite trends. Molecular dynamics simulations are employed to explore the effect of the TBS gradient on the deformation behavior of this nanomaterial. In this study, it is found that the strength of IGNT copper increases with a larger TBS gradient. By analyzing the microstructural characteristics, it is observed that as the TBS gradient increases, the dislocation density gradually decreases and the fraction of hexagonal close-packed atoms increases, leading to enhanced material strength. Additionally, with a higher TBS gradient, the appearance of hexagonal close-packed atomic lines traversing the grains effectively hinders dislocation motion, further improving the material's strength. In this research, new insights are offered into the design of gradient nanotwinned copper structures and important theoretical support and guidance are provided for enhancing the mechanical properties of gradient nanotwinned copper.