Thermal Decomposition Behavior of Expandable Pattern Including Blended Metal or Metal Oxide Powder in Evaporative Pattern Casting of Al-Si System Alloy

Abstract

We investigated thermal decomposition behavior of expanded patterns including thermal decomposition accelerators such as Ni, NiO, CuO and Cu₂O (hereinafter referred to as “powder-blended expanded patterns”) in an aluminum alloy evaporative pattern casting process; the following results were obtained. When these metal or metal oxide powders were blended in EPS (expandable polystyrene) patterns, an exothermic reaction occurred between metal or metal oxide powder and aluminum alloy melt. This reaction prevented, temperature drop at the top of the melt flow. In addition, these kinds of powder accelerated pattern thermal decomposition. As a result, the pattern thermal decomposition gas volume increased and aluminum alloy melt filling decreased.