DEVELOPMENT OF Al-Si ALLOY HYBRID COMPOSITE REINFORCED WITH ZINC OXIDE, SILICON CARBIDE AND GRAPHITE

Abstract

In this research work, the feasibility of developing Al-Si alloy hybrid composite reinforced with zinc oxide, silicon carbide and graphite using improved stir casting techniques with competing mechanical and wear properties as a potential substitute material for cast iron cylinder liner (sleeve) of an automobile engine was investigation. Zinc oxide, silicon carbide and graphite mixed in a varied weight ratios were used to prepare 7%, 9% and 11% hybrid reinforced Al Si alloy based composites by adopting two-steps stir casting techniques with three different speeds of 200, 300 and 500rpm. The mechanical properties of the composites produced were assessed by micro hardness test, tensile test, toughness; wear test and scanning electron microscopy equipped with EDX. The experimental and theoretical density values were in close range with a maximum level of 3.62% porosity. The results show that hardness increased with an increase in weight ratio of zinc oxide, and silicon carbide particulates in the composite; and with high weight ratio of graphite content, the effect of graphite on the hardness decline significantly. The tensile strength of grade six composite (16.7%ZnO+50%SiC+33.3%Graphite) was observed to be higher than composites grades with high weight ratio of graphite. The fracture toughness increases in relative to weight ratio of ZnO and SiC particulate and consequently depreciates with varied weight ratio of graphite. The % elongation for the entire composite grades was within the range of 1.03-3.45% and the values were invariant to the graphite content. Grade seven component 3%ZnO+16.7%+50%Graphite) exhibited lower wear susceptibility in comparison to all other Grades. The SEM micrographs equipped with EDX show satisfactory levels of uniform distribution of zinc oxide, silicon carbide and graphite particulates in Al-Si alloy matrix. Engine test-composite performance evaluation; weight reduction evaluation shows that substantial weight reduction of 61% has been achieved. The behaviour and performance of the sleeves during engine test show an indication of applicability in a typical automobile engine.