Observations on the Thermal Response and Mold Filling Behavior of an AZ91E Magnesium Alloy Cast by the Lost Foam Casting Process

摘要

Magnesium alloys are increasingly used for automotive and aerospace applications where the overall vehicle weight is a critical design parameter. Recent developments in Lost Foam Casting (LFC) of magnesium alloys demonstrated its suitability as an alternative process for near-net-shape manufacturing of these alloys. Utilizing thermal analysis techniques, research into the solidification mechanism of a magnesium alloy AZ91E cast by LFC process was carried out. Process parameters, such as: foam characteristics, pouring temperature, casting section thickness and application of vacuum were correlated with the casting cooling rate. Further, these parameters were related to the mold fillability and defect formation. The results indicate that the application of vacuum significantly influenced the alloy cooling rate, which caused the castings to solidify inhomogeneously, with partially solidified metal chunks present in the casting interior. Also, casting porosity increased in vacuum castings due to the entrapment of liquid-EPS pyrolysis products.