A New Insight to Dynamic Oxidation of Molten Metals by the Parametric Study of Oxide/Metal/Oxide Sandwich Formation

摘要

The high tendency of aluminum and magnesium to oxidation challenges the production of reliable cast parts due to the formation of double oxide film-related defects. Investigating the issue, the dynamic oxidation which occurs in the pouring step would be the main concern. To characterize the dynamically formed oxide films, the so-called oxide/metal/oxide (OMO) sandwich method is suggested. In this method, blowing two separate bubbles into the melt causes the formation of a sandwich sample consisting of two oxide films and a layer of entrapped metal between them. Shape, velocity and rising behavior of the blown bubbles play an important role in the production of oxide/metal/oxide sandwiches. The behavior of the bubbles was investigated in two media, water and sunflower oil. The obtained results were used to determine the proper pressures of the air blown in the melt. The casting process is simulated by computer software to ensure that the mold cavity will be filled without melt turbulence via the designed gating systems. By determining the proper values for the effective parameters in producing OMO sandwiches, the casting process was done. After the solidification processes, samples were examined via X-ray radiography to get a clear picture of the location of the bubbles. Eventually, the OMO sandwiches were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).