Abstract Tensile and creep responses of Cu-Nb composites are predicted at 400 ° C using a high-temperature discrete dislocation plasticity (DDP) framework where the multilayer composites are idealized as two-dimensional unit cells with periodic boundary conditions. Considering the fact that the interfaces in multilayer composites dominate their plastic response, bi-material interfaces are treated here so as to store lattice dislocations via formation of steps at the interfaces. While dislocations in the Nb layer are assumed to move by glide only at 400 ° C , they move by a combination of glide and climb in the Cu layer at this temperature. Material parameters for the layers are obtained at 400 ° C by fitting the DDP predictions of the tensile response of Cu-Nb composites to the experimental data corresponding to the composites with the layer thickness in the range 65 nm ≤ h ≤ 2 μ m . Using these material parameters, the framework enables quantitative predictions of the creep responses of these composites at 400 ° C , which are in very good agreement with the available experimental data. Investigations of the results demonstrate that: (i) the creep response of Cu-Nb composites, in line with observations, is dependent on the laminate length scale h as well as on the stress indicating that the creep behavior is dislocation dominated; (ii) the average stresses within the layers remain almost unchanged (with some fluctuations) during the time history indicating that there is a limited load transfer between the Nb and Cu layers during the creep process; and (iii) the dislocation and step densities in the Cu layers are higher than those in the Nb layers implying that the interfaces interact with a high flux of climbing dislocations from the Cu layers. Predictions of the deformed shapes of the Cu-Nb composites including the deformed configurations of the interfaces imply that annihilation of climbing Cu dislocations at the interfaces is the dominant interaction mechanism that occurs at the interfaces. This recovery mechanism in the bi-material interfaces facilitates dislocation generation and movement in the Cu layers and thus enhances the creep strains.

中文翻译：

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Cu-Nb 复合材料的高温拉伸和蠕变行为：离散位错塑性研究

摘要 Cu-Nb 复合材料的拉伸和蠕变响应在 400 °C 下使用高温离散位错塑性 (DDP) 框架进行预测，其中多层复合材料被理想化为具有周期性边界条件的二维晶胞。考虑到多层复合材料中的界面主导了它们的塑性响应这一事实，双材料界面在这里被处理，以便通过在界面处形成台阶来存储晶格位错。虽然假设 Nb 层中的位错仅在 400°C 时通过滑动移动，但在此温度下它们通过在 Cu 层中滑动和爬升的组合移动。通过将 Cu-Nb 复合材料的拉伸响应的 DDP 预测与对应于层厚度范围为 65 nm ≤ h ≤ 2 μm 的复合材料的实验数据进行拟合，可以在 400°C 下获得这些层的材料参数。使用这些材料参数，该框架能够定量预测这些复合材料在 400°C 下的蠕变响应，这与可用的实验数据非常吻合。结果的研究表明： (i) Cu-Nb 复合材料的蠕变响应与观察结果一致，取决于层压长度尺度 h 以及表明蠕变行为以位错为主的应力；(ii) 层内的平均应力在时间历程中几乎保持不变（有一些波动），表明蠕变过程中 Nb 和 Cu 层之间的载荷转移有限；(iii) Cu 层中的位错和台阶密度高于 Nb 层中的位错和台阶密度，这意味着界面与来自 Cu 层的攀爬位错的高通量相互作用。包括界面变形构型在内的 Cu-Nb 复合材料变形形状的预测意味着界面处攀爬 Cu 位错的湮灭是发生在界面处的主要相互作用机制。双材料界面中的这种恢复机制促进了 Cu 层中位错的产生和移动，从而增强了蠕变应变。