Nickel-based superalloys are usually exposed to high static or cyclic loads in non-ambient environment, so a reliable prediction of their mechanical properties, especially plastic deformation, at elevated temperature is essential for improved damage-tolerance assessment of components. In this paper, plastic deformation in a single-crystal nickel-based superalloy CMSX4 at elevated temperature was modelled using discrete dislocation dynamics (DDD). The DDD approach was implemented using a representative volume element with explicitly-introduced precipitate and periodic boundary condition. The DDD model was calibrated using stress–strain response predicted by a crystal plasticity model, validated against tensile and cyclic tests at 850 °C for <001 > and <111 > crystallographic orientations, at a strain rate of 1/s. The DDD model was capable to capture the global stress–strain response of the material under both monotonic and cyclic loading conditions. Considerably higher dislocation density was obtained for the <111 > orientation, indicating more plastic deformation and much lower flow stress in the material, when compared to that for <001 > orientation. Dislocation lines looped around the precipitate, and most dislocations were deposited on the surface of precipitate, forming a network of dislocation lines. Simple unloading resulted in a reduction of dislocation density. Plastic deformation in metallic materials is closely related to dynamics of dislocations, and the DDD approach can provide a more fundamental understanding of crystal plasticity and the evolution of heterogeneous dislocation networks, which is useful when considering such issues as the onset of damage in the material during plastic deformation.

中文翻译：

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使用离散位错动力学模拟单晶镍基高温合金中的塑性变形

镍基高温合金通常在非环境环境中承受高静态或循环载荷，因此，对高温下其机械性能（尤其是塑性变形）进行可靠的预测对于改进组件的耐损伤性评估至关重要。在本文中，使用离散位错动力学（DDD）对单晶镍基高温合金CMSX4在高温下的塑性变形进行了建模。DDD方法是使用具有代表性的体积元素以及明确引入的沉淀和周期性边界条件实现的。使用由晶体可塑性模型预测的应力-应变响应对DDD模型进行校准，并针对在850°C下<001>和<111>晶体取向的拉伸和循环测试进行了验证，应变率为1 / s。DDD模型能够捕获材料在单调和循环载荷条件下的整体应力-应变响应。与<001>取向相比，<111>取向获得了更高的位错密度，表明材料中出现了更大的塑性变形和更低的流动应力。位错线在沉淀物周围成环，大多数位错沉积在沉淀物表面，形成位错线网络。简单的卸载导致位错密度的降低。金属材料中的塑性变形与位错动力学密切相关，而DDD方法可以提供对晶体可塑性和异质位错网络演变的更基本的了解，