Center for Advanced Vehicular Systems

Spotlight on Research - Casting/Solidification of Magnesium Alloys

Researchers: Sergio Felicelli, John Berry, Liang Wang, and Hongjoo Rhee

Magnesium alloy cast parts are gaining increasing attention from the automotive sector where the aim is weight reduction. However, the casting of magnesium alloys is still plagued with problems that are difficult to solve: porosity, macrosegregation, oxide entrainment, irregularity of microstructure, corrosion, machining safety, etc. This research project addresses the fundamental behavior of solidification phenomena that lead to undesired defects (e.g., porosity, macro-segregation, mushy zone) in magnesium cast parts, with the objective of developing new or improved casting methods for these alloys.

The results of this study revealed the existence of abundant oxide film defects, similar to those observed in aluminum alloys. Remnants of oxide films were detected on some pore surfaces, and folded oxides were observed in fracture surfaces indicating the presence of double oxides entrained during pouring. The following figure shows that Scanning Electron Microscope (SEM) image of oxide films on two opposite sides of a fracture surface of a tensile test specimen taken from AZ91 sample.