Effect of calcium on mechanical properties of recycled aluminiumcasting alloys

Abstract

The effect of the addition of calcium on tensile properties, fracture toughness, and fatigue characteristics was investigated in JIS AC4C-T6, JIS AC2B-T6, and JIS AC4D–T6 aluminium casting alloys with various iron contents. The number of coarse platelike Al-Fe based intermetallic compounds increased with increasing iron content. The modification of the eutectic silicon morphology is successfully achieved by the addition of 40 ppm calcium. The addition of calcium makes the shape of the intermetallic compound, as well as the eutectic silicon, finer and round, and this seems to contribute to the improvement of mechanical properties, i.e. elongation, Charpy absorbed energy, both impact and conventional fatigue strengths, dynamic fracture toughness, and impact fatigue fracture toughness. Impact fatigue strength, especially in the high cycle region, increases with the addition of calcium. In the lower stress high cycle fatigue region, a higher fatigue strength with increasing iron content is observed owing to the deflected crack path along Al-Fe based intermetallic compounds.