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

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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.