Microstructure and Properties of Squeeze Cast AC8A MMC Reinforced with Ni-aluminide

용탕단조한 Ni-aluminide 보강 AC8A기 복합재료의 조직 및 특성

AC8A matrix composites reinforced with Ni-aluminide were fabricated by squeeze casting process, and the characteristics and nature of the growth of Ni-aluminide phases at the interface between nickel and aluminurn were investigated. In the as-cast composites, the reaction layer between Ni skeleton and aluminum matrix was found to be $NiAl_3$, regardless of the casting temperatures and the kinds of preforms. During high temperature solution treatment the $NiAl_3$ layer grew and formed new $Ni_2Al_3$ layer. Because of presence of the porosity formed by Kirkendall effect at the interface between $NiAl_3$ and aluminum matrix, the tensile strength of composites was inferior to that of AC8A matrix alloy. However, the composites exhibited superior wear resistance due to the formation Ni-aluminide intermetallic phases. Composite A, of which Ni skeleton was fully transformed into Ni-aluminide, shows better wear resistance than that of composite B which still possessed some unreacted Ni skeleton.