Process-Structure Relationships of Magnesium Alloys

This research study characterizes the effects of solidification conditions on the resulting microstructure of an AM60B magnesium alloy during the solidification cycle of the casting. Seventeen control points are chosen from different sections of an instrument panel beam casting and its centerline coordinates are located. These control points locations are then used by Meridian Lightweight Technology Inc. to run a simulation in a MAGMASoft casting software to obtain temperature-time specific data. An exact analytical solution to the Stefan problem is used to compute the one dimensional heat transfer for a section of the casting and to calculate its temperature distribution along the thickness, during solidification. Next, the cooling rates are calculated with respect to its distance from the mold wall of the casting. Finally a generalized relationship between the cooling rate and the grain size of different casting processes is developed in the form of a mathematical model. This model is used in concurrence with the analytical solution to determine the extent of skin thickness formed during solidification and the grain size distribution in the section of a high pressure die-cast instrument panel beam