Connecting Oxide Bifilms' Properties from Atomistic Simulations with Virtual Casting of Aluminum

AluminumAluminumoxide bifilmsBifilms, formed during melt turbulence flow, can have a significant detrimental effect on material properties after they are entrapped in the final cast products. Recently, molecular dynamics (MD) simulations were used to simulate the formation and fracture mechanisms of bifilmsBifilmsat the nano-scale, which are hard to obtain experimentally. The results showed that the fracture occurred at the Al/oxide interface instead of the oxide/oxide interface for both amorphous oxide and crystalline α-Al2O3, which represent the “young” and “old” oxides referred in aluminumAluminumcastingCasting. The fracture energy is higher for the α-Al2O3 bifilm. However, if OH-termination contamination occurs due to residue hydrogen gas and water trapped in the aluminumAluminumoxide bifilmBifilm (BI)interface, the OH-termination oxide bifilmBifilm (BI)fractured at the oxide/oxide interface and with a much-reduced fracture energy. This is consistent with the general picture that oxide bifilmsBifilmswill initiate cracks, especially fatigueFatiguecracks in cast aluminumAluminumproducts. For macroscopic models, crack initiation and propagation can be modeled by cohesive zone method. Therefore, we propose a simple size bridging relationship to connect the MD-predicted oxide bifilmsBifilmsfracture energy and fracture strength with future finite element modeling.