Solidification and Casting in Aerogels

摘要

Recent advances in solidification of eutectic and off-eutectic alloys achieved with a new type of solidification furnace based on the use of aerogels are described. The aerogels are highly porous, transparent, non-wetting ceramic materials. We show that in eutectic Al-Al_3 Ni alloys the Al_3Ni fibres undergo an order-disorder transition in their spatial arrangement if the solidification front is accelerated in a controlled way. On acceleration the fibres are ordered whereas with deceleration the disorder increases. In Al-Si eutectic and off-eutectic alloys no effect of controlled acceleration was observed on the interlamellar spacing of the Si-plates. Experiment with ternary Al-Si-Mg alloys will be presented concerning the effect of acceleration on the mush evolution compared to stationary solidification conditions. Finally we present new developments on block moulding and investment casting using a new type of composite aerogel based material made from classical sands and organic aerogels.