MECHANICAL PROPERTIES OF CAST HYPOEUTECTIC AL-SI ALLOY IN HEXACHLOROETHANE-COATED MOULD

This work investigated the effect of hexachloroethane coated mould on the mechanical properties of hypoeutectic aluminium silicon alloy. An alumina based mould coating containing varying proportion (5% to 30%) of volatile hexachloroethane, C2Cl6 was prepared. The prepared mould coating was applied to form a coat of 2mm thick on the prepared metallic mould. The hypoeutectic aluminium-silicon alloy melted at 50(circle)C superheat was poured into the already prepared coated mould and allowed to solidify. Then the effects of the volatile hexachloroethane, C2Cl6 concentration on the grain size, ultimate tensile strength (UTS), 0.2% Proof Stress, Hardness, percentage elongation and percentage reduction in area of the cast hypoeutectic aluminium-silicon alloy were assessed. The study revealed that the increase in C2Cl6 concentration in the mould coating up to 15 wt.% decreases the grain size of the alloy thereby causing increase in the mechanical properties (UTS), 0.2% proof stress, hardness, percentage elongation and percentage reduction in area) of the alloy. It was established that the optimum value of C2Cl6 concentration at which the mechanical properties were optimum is about 15 wt.%. Beyond this value, the C2Cl6 becomes deleterious to grain refinement due to rapid agitation in the mould.