Solidification and metallurgical phenomena in lost foam casting of aluminum alloys

Abstract

The lost foam process has generated considerable interest among foundrymen because of the inherent advantages associated with the production of the casting. It has been predicted that the number of foundries utilizing this innovative process will continue to increase rapidly over the next few years. The principal feature of this casting technique is the use of foamed polymer patterns for the production of the component. On contact with the liquid metal, the polymer pattern undergoes thermal degradation through a series of complex transitions to produce liquid and gaseous degradation products. The formation of these degradation products in the mold has a significant effect on the solidification behavior and on the microstructural parameters. Furthermore, the interaction of the degradation products with the solidifying metal may introduce various defects in the casting which are unique to this process. The fundamental aspects associated with the solidification of lost foam castings have been described. The effects of polymer degradation on microstructural characteristics and on defects have been discussed.