Aluminium-silicon castings are typically produced by gravity casting. Bottom gated systems are usually required if surface turbulence is to be eliminated. Latest research has demonstrated, that for every liquid metal there is critical velocity above which the surface will fold over and entrain itself in the bulk of the metal. Therefore the strength properties the aluminium castings are largely determined by microstructural defects, particularly pores and oxide films which are created by surface turbulence. The purpose of this paper is to investigate tensile properties and microstructure of aluminium alloy in a casted state two different designs of gating system. The first is the usual bottom gating system and the second is novel design of gating system named a vortex-gate introduced by Campbell [1]. The results of the mechanical tests revealed that there is a small improvement in ultimate tensile strength for vortex-gate design of pouring system. The oxide film defects were observed in microstructure of a sample taken from poured casting by using the bottom gated system.
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