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首页> 外文期刊>Journal of the Mechanics and Physics of Solids >A unified mechanistic model for Hall-Petch and inverse Hall-Petch relations of nanocrystalline metals based on intragranular dislocation storage
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A unified mechanistic model for Hall-Petch and inverse Hall-Petch relations of nanocrystalline metals based on intragranular dislocation storage

机译：基于intragranulation脱位储存的纳米晶金属的霍尔 - Petch和逆霍尔 - PACH关系的统一机制模型

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Nanocrystalline (NC) metals often show transition from Hall-Petch (HP) strengthening to inverse HP softening as the average grain size decreases below a critical value. Compared to the HP behavior whose mechanism is well understood as the dislocation pile-up at grain boundaries (GBs), several hypotheses have been proposed to explain the veiled inverse HP behavior and no consensus has been reached yet. In this work, we propose a size-dependent model considering the influence of grain size on the intragranular dislocation storage ability and unify the HP and inverse HP relations for NC metals. The reduction of the intragranular dislocation storage ability with decreasing grain size is revealed as the underlying mechanism of the breakdown of the HP behavior in NC. Prediction of the critical grain size of 26.9 nm for the HP-inverse HP transition of NC copper agrees well with experimental results. Numerical results suggest that the harmonized deformation of GB and grain interior (GI) dominates the remarkable ductility enhancement of NC metals in the inverse HP region. Moreover, our results suggest that the formation of dimple structures spanning several grains at fracture surfaces of NC metals is attributed to the coalescence of inter- and intra-granular microcracks and microvoids in clustered grains with Goss texture in local shear bands. As the GB strength increases, NC metals show enhancement in yield strength and delay in occurrence of the inverse HP behavior. Our studies give new insight into the contribution of GB sliding to the plastic behaviors of NC metals, and provide valuable guidance for the rational design of NC metals with high ductility and high strength.
机译：纳米晶（NC）金属通常显示从霍尔 - 取出（HP）的过渡强化转向逆HP软化，因为平均晶粒尺寸降低低于临界值。与其机制良好理解为谷物边界（GBS）的脱位堆积的惠普行为相比，已经提出了几个假设来解释遮盖的反相HP行为，并且尚未达成共识。在这项工作中，考虑到晶粒尺寸对胚胎脱位储存能力的影响，提出了一个依赖依赖性模型，并统一了NC金属的惠普和反向惠普关系。随着晶粒尺寸降低的术语脱位储存能力的降低被揭示为NC中HP行为分解的潜在机制。对于NC铜的HP - 反相HP转变，NC铜的临界粒度的预测与实验结果吻合良好。数值结果表明，GB和谷物内部（GI）的统一变形主导了反相HP区域中NC金属的显着延展性。此外，我们的研究结果表明，在NC金属的断裂表面处形成跨越多个晶粒的凹坑结构归因于局部剪切带的聚集粒细胞内粒细胞和中粒细胞间微裂纹和微系机的聚结。随着GB强度的增加，NC金属显示出屈服强度和延迟发生反相HP行为的增强。我们的研究提供了新的洞察GB滑动到NC金属的塑性行为的贡献，为NC金属的合理设计提供了高延展性和高强度的有价值指导。

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