Evolving dislocation cores at Twin Boundaries: Theory of CRSS Elevation
Evolving dislocation cores at Twin Boundaries: Theory of CRSS Elevation
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DOI：
10.1016/j.ijplas.2021.103141
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发表时间：
2021-11
影响因子：
9.8
通讯作者：
O. Celebi;A. Mohammed;J. Krogstad;H. Sehitoglu
中科院分区：
文献类型：
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作者：
O. Celebi;A. Mohammed;J. Krogstad;H. Sehitoglu
可孪生材料卓越的机械响应从根本上来说是由于位错孪晶边界 (D-TB) 反应导致临界解析剪切应力 (CRSS) 的升高。这些反应表现出丰富的多样性，具有多种可能的结果，并且表现出对微观结构特性的复杂依赖性，导致最先进的模型依赖于经验势或孪生相互作用参数对每个反应进行个案模拟。我们开发了一种没有经验主义的分析“演化位错核心”（EDC）模型，能够在给定微观结构特性（弹性常数、孪晶学等）的情况下预测任何反应的 CRSS 升高。该方法从根本上植根于完全各向异性框架内的能量最小化，揭示了位错核心随反应进展的演变。文献中首次提出了反应中复杂位错（例如阶梯杆）的核心结构，作为分布在滑移平面和孪晶平面上的不重合的非平面复合材料。该模型适用于多种面心立方 (FCC) 材料（Pb、Ag、Cu、Ni-Co 合金和 Ni-Ti 合金以及高熵合金 FeNiCoCrMn）中的多重滑移并入反应。预测的 CRSS 高程与原子模拟 (Ni) 和实验 (FeNiCoCrMn) 一致。该模型进一步建立了高程与不稳定堆垛/孪晶断层能量和固位错伯格斯矢量大小之间的强相关性，同时揭示了与作为共同基准的稳定内在堆垛层错能量的较差相关性。因此，本研究中开发的分析 EDC 模型增进了对多个前沿滑移孪生相互作用的理解，同时作为材料设计中 CRSS-elevation 工具的有效预测模型。
Superior mechanical response of twinnable materials fundamentally arises from an elevation of Critical Resolved Shear Stresses (CRSS) due to Dislocation-Twin Boundary (D-TB) reactions. These reactions exhibit rich variety with several possible outcomes and exhibit complex dependence on microstructural properties, causing state-of-the-art models to adopt a case-by-case simulation of each reaction relying on empirical potentials or twin-interaction parameters. We develop an analytical “Evolving Dislocation Core” (EDC) model devoid of empiricism, capable of predicting the CRSS-elevation for any reaction, given the microstructural properties (elastic constants, twin crystallography, etc.). The approach is fundamentally rooted in energy-minimization within a fully-anisotropic framework revealing the evolution of dislocation cores with progression of the reaction. The core-structure of complex dislocations (e.g. stair-rod) in the reaction is proposed, for the first time in literature, as a non-planar composite of disregistries distributed on slip and twin planes. The model is applied to multiple slip-incorporation reactions in several Face-Centered-Cubic (FCC) materials (Pb, Ag, Cu, Ni-Co alloys and Ni-Ti alloys and high-entropy alloy FeNiCoCrMn). The predicted CRSS-elevations show agreement with atomistic simulations (Ni) and experiment (FeNiCoCrMn). The model further establishes a strong correlation of the elevation with unstable stacking/twinning fault energy and the magnitude of the sessile dislocation's Burgers vector, while revealing poor correlation with the stable intrinsic stacking fault energy which is a common benchmark. Thus the analytical EDC model developed in this study advances understanding of slip-twin interactions on multiple fronts while serving as an effective predictive model for CRSS-elevation instrumental in materials design.