Abstract
With their excellent mechanical properties, Cu/Ta metallic nanolayered composites (MNCs) are extensively applied in aerospace and nuclear industry facilities. However, shear localization severely disrupts the ability of these materials to deform uniformly, attracting many researchers. The necessary time and length conditions of experiments limit the investigation of shear localization; thus, relevant studies are insufficient. The molecular dynamics simulation perfectly corresponds to the short duration and high strain rate of the deformation process. Therefore, in this study, we used molecular dynamics simulations to explore the effect of layer thickness on the shear localization of Cu/Ta MNCs with Kurdjumov–Sachs (KS) orientation–related interfaces. Our research demonstrates that shear localization occurs in samples with layer thicknesses below 2.5 nm, resulting in an inverse size effect on the flow strength. The quantitative analysis indicates that the asymmetry of dislocations in the slip transmission across the interface causes interface rotation. This activates dislocations parallel to the interface to glide beyond the distance of individual layer thicknesses, eventually forming shear bands. Both interface rotation and sliding dominate the plastic deformation in the shear band region. In addition, the dislocation density and amorphous phase increase with decreasing layer thickness.
Highlights
Cu matrix metallic nanolayered composites (MNCs), with their excellent mechanical behaviors, are extensively applied in aerospace and nuclear industry facilities [1–3]
In indentation tests of Cu/Ta MNCs, the results show that the shear distance of grain boundary sliding or rotation, caused by layer buckling beyond the layer thickness, results in the formation of shear bands [16]
Compared to the defect-free simulated samples, the experimental samples contain dislocations prior to deformation. They are more prone to activation under stress, which results in the yield strength being lower than the peak strength of the simulated stress–strain curve
Summary
Cu matrix metallic nanolayered composites (MNCs), with their excellent mechanical behaviors, are extensively applied in aerospace and nuclear industry facilities [1–3]. The plastic instability of Cu matrix MNCs produced by their shear localization severely disrupts the ability of the material to deform uniformly, limiting its application [5–9] To effectively control this instability, the process of shear bands (SBs) formation in Cu matrix MNCs needs to be explored. This research on rolled Cu/Nb multilayers showed that significant plastic instability was observed at a 4 nm layer thickness, while the 40 nm samples could deform uniformly with no shear band formation [18]. The length–scale dependency of shear localization mentioned above has not been investigated in Cu/Ta MNCs. In this study, the deformation behavior and mechanical properties of Cu/Ta MNCs with KS orientation-related interfaces were investigated. This study found that the plastic instability of Cu/Ta. MNCs has a significant length–scale dependency, with shear band formation and material softening observed in samples below the critical thickness. We expect to provide a valuable result for understanding the formation of plastic instability in Cu/Ta MNCs
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