Collaborative Research: Learning Microstructure- and Temperature-Dependencies of Grain Boundary Plastic Deformation Localization via Multi-modal In situ Characterization

非技术摘要：工程合金零件中的许多失效机制与变形如何通过组成零件的微观晶体(颗粒)之间的边界传递有关。尽管进行了广泛的研究，但对于变形将和不会跨越晶界传播的条件，仍然难以找到明确的实验证据，特别是在太空旅行或高超音速推进过程中发现的极端温度条件下。新的电子显微镜和X射线测量，可以详细地观察样品表面及其下方，正在一起使用，以观察变形是如何在发生时跨越晶界传播的。利用这些测量和机器学习技术，正在建立一套规则，描述变形如何作为温度的函数在代表各种常用结构合金的一系列模型原子晶体结构中传递。这些规则可以用来改进现有合金在该领域的使用，并设计新的高性能合金系统。技术摘要：利用最先进的原位表征技术来了解控制立方工程合金晶界及其附近塑性变形局部化的微观结构条件的温度相关性。能够同时探测微机械响应和微结构状态的现场表征技术(扫描电子显微镜中的高分辨率数字图像相关和基于同步辐射X射线的3D重建)的互补组合正被用于询问模型面心立方(FCC)和体心立方(BCC)合金中跨GB的微结构配置的高维空间。现有的机器学习(ML)工具还被用于对在每次原位实验中探索的大量微结构对进行自动分类，并学习预测GBs的塑性变形局部化行为随温度和相关变形机制激活的演变的标准。在这项工作中，通过低温变形激活孪生及其对GB塑性变形局部化的影响被用来创建一个通用框架，利用该框架可以评估其他变形机制的激活效果，如爬升、交叉滑动和GB滑动。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARY:Numerous failure mechanisms in engineering alloy parts are correlated to how deformation is transmitted across the boundaries between the microscopic crystals (grains) that comprise the part. Despite extensive study, definitive experimental evidence of the conditions at which deformation will and will not transmit across grain boundaries is elusive, particularly at extreme temperatures in conditions found during space travel or hypersonic propulsion. New electron microscopy and X-ray measurements, which can look in detail at and below the sample surface, are being used together to watch how deformation is transmitted across grain boundaries as it occurs. Using these measurements and machine-learning techniques, a set of rules are being established describing how deformation is transmitted as a function of temperature in a range of model atomic crystal structures representing various forms of commonly used structural alloys. These rules can then be used to improve the usage of existing alloys in the field and to design new high-performance alloy systems.TECHNICAL SUMMARY:State-of-the-art in situ characterization techniques are being taken advantage of to learn the temperature-dependence of microstructural conditions governing plastic deformation localization at and near grain boundaries (GBs) in cubic engineering alloys. A complimentary combination of in situ characterization techniques (high-resolution digital image correlation in the scanning electron microscope and synchrotron X-ray-based 3D reconstructions) capable of probing micromechanical response and microstructural state simultaneously are being used to interrogate the high-dimensional space of microstructural configurations that can exist across GBs in model face-centered cubic (FCC) and body-centered cubic (BCC) alloys. Existing machine-learning (ML) tools are also being used to perform automated classification of the large number of microstructural pairings probed during each in situ experiment and learn criteria for predicting the evolution of plastic deformation localization behaviors at GBs with temperature and associated deformation mechanism activation. In this effort, activation of twinning through cryogenic deformation and its effects on GB plastic deformation localization are being used to create a generalized framework with which the effect of activation of other deformation mechanisms, such as climb, cross-slip, and GB sliding, can be evaluated.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.