Plastic anisotropy and twin distributions near the fatigue crack tip of textured Mg alloys from in situ synchrotron x-ray diffraction measurements and multiscale mechanics modeling
Plastic anisotropy and twin distributions near the fatigue crack tip of textured Mg alloys from in situ synchrotron x-ray diffraction measurements and multiscale mechanics modeling
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DOI：
10.1016/j.jmps.2022.104936
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发表时间：
2022-05
影响因子：
5.3
通讯作者：
D. Xie;Wei Zhang;Z. Lyu;P. Liaw;H. Tran;H. Chew;Yujie Wei;Yang Ren;Yanfei Gao
中科院分区：
文献类型：
--
作者：
D. Xie;Wei Zhang;Z. Lyu;P. Liaw;H. Tran;H. Chew;Yujie Wei;Yang Ren;Yanfei Gao
尽管镁合金由于其优异的机械性能而具有许多潜在的应用，但主要由于我们对其失效机制的了解有限，仍然存在许多实际限制。微观结构尺度上的原位无损应变测量对于理解疲劳裂纹行为至关重要，这比基于复制技术的宏观测量和小尺度机械测试具有更大的优势，后者无法轻易提供许多与尺度相关的变形和失效机制的协同作用的完整视图。这项工作利用最先进的同步加速器 X 射线衍射技术，在高织构 ZK60 镁合金的疲劳裂纹尖端附近获得具有高空间分辨率的原位应变映射结果。将塑性区的精确测量结果与微机械建模框架进行比较，其中稳定疲劳裂纹通过不可逆的滞后内聚界面模型进行模拟，周围的塑性通过 Hill 各向异性塑性进行模拟。各向异性变形场的总体一致性达到了朝向裂纹尖端的塑性区尺寸的一半，而裂纹尖端的差异可用于开发反演模型，以在我们未来的工作中提取特定于材料的疲劳损伤演化。令人惊奇地注意到，无论这种织构合金的裂纹扩展方向如何，孪生活动都集中在从疲劳裂纹尖端到尾迹的窄带中。这种双裂纹相互作用可以通过我们的具有几个代表性晶体取向的晶体塑性有限元模拟来理解。
In spite of many potential applications due to their superior mechanical properties, magnesium alloys still find many practical restrictions primarily due to our limited knowledge of their failure mechanisms.In situand non-destructive strain measurements on the microstructural scales are critical in understanding the fatigue crack behavior, which has greater advantages than the macroscopic measurements based on replica technique and the small-scale mechanical testing that cannot easily provide a complete view on the synergy of many scale-dependent deformation and failure mechanisms. This work exploits the state-of-the-art synchrotron X-ray diffraction technique to attainin situstrain mapping results, with high spatial resolution, near a fatigue crack tip in the highly textured ZK60 Mg alloy. The accurate measurements in the plastic zone are compared to a micromechanical modeling framework, in which the steady fatigue crack is simulated by an irreversible, hysteretic cohesive interface model and the surrounding plasticity by Hill anisotropic plasticity. The general agreement in the anisotropic deformation fields is reached down to half of the plastic zone size towards the crack tip, while the discrepancy right at the crack tip can be used to develop an inverse model to extract the material-specific fatigue damage evolution in our future work. It is surprisingly noted that twin activities are localized in a narrow band from the tip to the wake of the fatigue crack, irrespective of the crack growth direction of this textured alloy. Such twin-crack interactions are understood here by our crystal plasticity finite element simulations with several representative crystallographic orientations.