NSF-Europe: Collaborative Modeling and Experiemental Research Program to Understand the Dynamics of Dislocation--Particle Interactions

本研究聚焦于原子到微观尺度，特别强调通过原子模型和动态原位和静态非原位透射电镜实验相结合，确定位错-颗粒相互作用的控制机制。分子静力学模拟将用于表征析出相的原子结构以及界面和位错核心结构，分子动力学将用于确定时间演化动力学。静态非原位电子显微镜将使用预变形材料来表征析出相的结构和化学性质，以及位错-析出相的相互作用。一个主要的目标是确定滑动位错和铝合金中不同析出相之间相互作用的性质，作为温度和应变的函数，并利用这些信息来模拟析出相硬化合金的力学性能。预变形材料将在不同温度下在电子显微镜下原位进一步变形，以确定反应途径和动力学。模拟和实验结果的相关性将提供空间和时间尺度范围内的信息，这些信息是其他方法无法获得的，但主导着观察到的响应。这种结合的方法将确定位错析出相互作用的动力学，作为应力、温度、析出形式和一致性的函数，包括识别位错相互作用后可能的晶体结构转变。研究的材料系统将从铝合金中提取，尽管这些发现可能适用于一系列系统。最终，所开发的位错-沉淀相互作用规则将被纳入更高长度尺度的模型中，以预测材料的力学响应。外国合作者一直在与主要研究人员合作，研究铁素体材料中富铜沉淀的结构和演化，以及它们在硬化中的作用，方法是使用原位和非原位电子显微镜，以及原子尺度的计算机模型。还建议创建适合年龄的教育模块，将结构与机械性能联系起来。本项目由美国国家科学基金会多学科活动办公室、材料研究部（金属研究）和国际办公室（西欧）共同资助，作为美国国家科学基金会与欧洲材料研究合作项目（NSF 02-135）。该项目是与英国牛津大学和利物浦大学合作进行的。

This research focuses on the atomic to the microscopic scale with a particular emphasis on identifying the controlling mechanisms of dislocation - particle interactions through a combination of atomistic modeling and dynamic in-situ and static ex-situ transmission electron microscopy experiments in Al-alloys. Molecular statics simulations will be used to characterize the atomic structure of precipitates and the interface and dislocation core structures, and molecular dynamics will be used to determine time evolution dynamics. The static ex-situ electron microscopy will use predeformed material to characterize the precipitate structure and chemistry, and dislocation-precipitate interactions. A major objective is to determine the nature of the interaction between glide dislocations and different precipitates in Al-alloys as a function of temperature and strain, and to use this information to model mechanical properties in precipitate hardened alloys. Predeformed material will be further deformed in situ in the electron microscope at different temperatures to determine reaction pathways and kinetics. Correlation of the simulation and experimental results will provide information over a range of spatial and temporal scales that are inaccessible to the other approach but dominates the observed response. This combined approach will determine the dynamics of dislocation precipitate interactions as a function of stress, temperature, precipitate form and coherency, including identifying possible crystallographic structural transformations following dislocation interactions.The material systems investigated will be drawn from Al-alloys, although the findings are likely to be applicable to a range of systems. Ultimately, the dislocation-precipitate interaction rules developed will be incorporated in higher length scale models to predict the mechanical response of materials. The foreign collaborators have been working with the principal investigators on the structure and evolution of copper-rich precipitates in ferritic materials, and their role in hardening by using a combination of in-situ and ex-situ electron microscopy, and atomic-scale computer modeling. It is also proposed to create age-appropriate educational modules to relate structure to mechanical properties.This NSF project is co-funded by the Office of Multidisciplinary Activities, the Division of Materials Research (Metals Research) and International Office (Western Europe) as a Cooperative Activity in Materials Research between the NSF and Europe (NSF 02-135). This project is being carried out in collaboration with Oxford and Liverpool Universities in UK.