Collaborative Research: Novel Atomistic-Continuum Simulation of Sequential Grain Boundary-Dislocation Slip Transfer Reactions

该奖项的研究目标是提出一种原子-连续介质耦合模拟方法来探索晶界滑移转移。缺乏这样的方法是目前在发展反映晶界结构和行为的本构关系方面取得进展的障碍，例如在多晶塑性方面。这个问题变得复杂起来，因为需要考虑位错场的长程相互作用，同时还需要考虑界面的原子级结构细节。这项研究将通过保持界面反应的完全原子分辨率并连续粗粒化远离界面的场描述来探索与双晶界面的顺序位错反应过程，这些距离通常是完全解析的分子动力学无法到达的。这种能力将使得能够在整个晶界自由度范围内对位错-晶界滑移转移反应进行参数研究，包括倾斜和扭曲的晶界，以及通常具有刻面结构并可以引起大量位错成核的不对称晶界。具有大范围孪晶间距的纳米孪晶结构也将被考虑。这项工作将使用最先进的嵌入原子方法势，对于铜等面心立方金属，它在模拟位错成核、层错形成和位错相互作用的各个方面都被证明是相当准确的。这项研究将提出一种将纳米尺度金属行为的完全原子化描述与细观和宏观尺度本构行为相结合的计算方法。它将允许研究多晶金属中位错和晶界之间发生的复杂相互作用，这将导致基于物理的金属预测本构模型。这项研究将推动金属的多尺度建模，并导致改进的模拟和最终的材料设计。研究结果将被纳入两所大学的研究生课程。

The research objective of this award is to advance a coupled atomistic-continuum simulation method to explore slip transfer at grain boundaries. Lack of such a method is a current obstacle to progress towards developing constitutive relations that reflect the structure and behavior of grain boundaries, for example in polycrystal plasticity. The problem is complicated by the need to account for long range interactions of dislocation fields while also considering the atomic-level structural detail of the interface. This research will explore processes of sequential dislocation reactions with bicrystal interfaces by maintaining full atomistic resolution of the interface reactions and successively coarse graining the field description away from the interfaces at distances that are normally inaccessible to fully resolved molecular dynamics. Such a capability will enable parametric studies of dislocation-grain boundary slip transfer reactions over the full range of grain boundary degrees of freedom, including tilt and twist boundaries, as well as asymmetric boundaries that often have faceted structure and can give rise to profuse dislocation nucleation. Nanotwinned structures with a wide range of twin spacing will also be considered. This work will use state-of-the-art embedded atom method potentials which have proven quite accurate for fcc metals such as Cu in modeling various aspects of dislocation nucleation, formation of stacking faults, and dislocation interactions This research will advance a computational method that couples fully atomistic descriptions of nanoscale metallic behavior to mesoscale and macroscale constitutive behavior. It will permit study of the complex interactions that occur between dislocations and grain boundaries in polycrystalline metals which will lead to physics-based predictive constitutive models for metals. This research will advance the multiscale modeling of metals and lead to improved simulation and ultimately design of materials. Results of the research will be incorporated into graduate courses at both institutions.