Understanding Origination and Evolution of Solidification Defects in Aluminum Alloy Manufacture: Integrating Computational Models and In-situ Casting Experiments

开发用于汽车和航空航天工业结构部件的高性能铝合金需要全面了解这些合金制造过程中的缺陷演变。由所谓的氧化膜（即折叠的氧化层）引起的凝固缺陷大大削弱了通过铸造、焊接或增材制造制造的零件的机械强度。本项目旨在通过将铝合金铸件的定量计算模型与新实验相结合，科学地研究凝固缺陷在加工过程中的产生和演变过程。揭示缺陷形成的基础科学将更好地指导使用凝固的制造工艺的发展和改进。该项目还将对不同阶段的学生教育产生重大影响，例如向K-12学生介绍计算和实验方法，让本科生和研究生参与研究，并在多个层面的相关课程中纳入本研究的新主题。此外，该项目将为相关铝行业提供及时的科学数据和结果。金属合金制造过程中氧化膜的形成和演化机理十分复杂，但其对合金凝固过程中纳米组织和微观组织的影响尚不完全清楚。本研究项目的总体目标是从根本上研究与氧化物生物膜相关的凝固缺陷，如气体孔隙度，并研究它们对铝合金凝固过程中相成核过程和枝晶结构形成的影响。氧化物和氧化物膜与固化熔体的纳米级相互作用以及对相成核过程（结晶、半结晶或非晶）的影响将通过进行数十亿原子分子动力学模拟来揭示。通过大规模相场模拟，在微畴中发现氧化膜的演化过程、与凝固枝晶的相互作用以及由此形成的缺陷。先进的原位x射线成像和非原位电子显微镜铸造实验将验证和基准计算模型。综合计算-实验方法将在铝合金凝固过程中缺陷的起源和演变方面取得无与伦比的发现。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Development of high-performance aluminum alloys for structural components in the automobile and aerospace industries requires comprehensive knowledge of defect evolution in manufacturing of these alloys. Solidification defects resulted from the so-called oxide bifilms (i.e., folded oxide layers) greatly weaken the mechanical strength of parts manufactured by casting, welding or additive manufacturing. This project aims to scientifically investigate how solidification defects originate and evolve during processing by integrating quantitative computational models with novel experiments for aluminum alloy casting. The fundamental science revealed on defect formation will better guide the development and improvement of manufacturing processes using solidification. The project will also have a strong impact on educating students at different stages such as introducing K-12 students to computational and experimental methodologies, involving undergraduate and graduate students in research, and including new topics from this research in relevant courses at multiple levels. Further, this project will provide timely scientific data and results to relevant aluminum industries.The physics of initiation and evolution of oxide bifilms in manufacturing of metallic alloys is highly complex, and yet, their effects on the nanostructures and microstructures developed during solidification are not fully comprehended. The overall objective of this research project is to fundamentally study solidification defects associated with oxide biofilms, e.g., gas porosity, and investigate their influence to the phase nucleation process and formation of dendritic structures in solidification of aluminum alloys. Nano-scale interactions of oxides and oxide bifilms with solidifying melt and the effects on the phase nucleation process (crystalline, semi-crystalline or amorphous) will be revealed by performing multi-billion atom molecular dynamics simulations. New discovery of the oxide bifilms evolution, their interactions with the solidifying dendrites, and consequent defects formed will be achieved in micro-domain by large-scale phase-field simulations. Advanced in-situ x-ray imaging and ex-situ electron microscopy in casting experiments will validate and benchmark computational models. The integrated computational-experimental approach will achieve unparalleled findings on the origination and evolution of defects during solidification of aluminum alloys.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.