Proposal Number: CTS-0553570 Principal Investigator: Felicelli, Sergio D. Affiliation: Mississippi State University Proposal Title: Modeling of Oxide Bifilms in Aluminum Castings
Oxide bifilms have recently gained much attention within the casting community. These defects, mainly found in aluminum alloy castings, are now thought to be the cause of micro-cracks, micro-porosity, and other ailments that greatly impair the mechanical properties of cast parts. While there is experimental evidence that is consistent with this hypothesis, the role of bifilms in producing defects and the mechanisms of defect creation are mostly speculative, because direct observation is extremely difficult; the mechanical properties of bifilms are unknown; and the physics of bifilm dynamics is not understood. Furthermore, the attempts to improve casting methods to reduce bifilm damage have had mixed success, and there is still controversy on how to deal with the bifilm issue. This research program will use a multiscale modeling approach with experimental validation to investigate the mechanisms by which oxide bifilms lead to porosity defects in aluminum castings. A solidification computer model will be developed to simulate porosity originated from oxide bifilms. Pore number and size distribution will be measured in experimental castings and compared with model predictions of bifilm final shapes and locations. A program objective is to provide conclusive evidence on the role of bifilms as originators of porosity. Complex bifilm dynamic events like furling, unfurling, opening, initiation of gas pores, and others, will be for the first time observed directly in a computer model. This will significantly advance the understanding of bifilm-related defects. By gaining insight in the physics of bifilms, better judgment can be made on how to avoid or reduce their negative effects and hence contribute to the design of improved casting methods. With respect to Broader Impacts, this research will directly impact aluminum casting technology and the ability of automotive and aerospace industries to produce high quality aluminum cast parts. The desired outcome of the program is to contribute to the manufacture of lighter and more energy-efficient vehicles. The significant involvement and education of graduate students and undergraduate students in the research will have an impact on a variety of people and is an important part of the project.