Influence of rice husk ash - Silicon carbide weight ratios on the mechanical behaviour of Al-Mg-Si alloy matrix hybrid composites

The influence of rice husk ash (RHA) and silicon carbide (SiC) weight ratio on the mechanical behaviour of Al-Mg-Si alloy matrix hybrid composites was investigated. RHA and SiC mixed in weight ratios 0:1, 1:3, 1:1, 3:1, and 1:0 were utilized to prepare 5, 7.5 and 10 wt% of the reinforcing phase with Al- Mg-Si alloy as matrix using two-step stir casting method. Density measurement, estimated percent porosity, tensile properties, fracture toughness, and SEM examination were used to characterize the composites produced. The results show that the composites were of good casting quality as the estimated porosity values were less than 2.5 % in all grades produced. For the three weight percent worked on, the tensile-, yield-, and specific strength decreases with increase in the weight proportion of RHA in the RHA-SiC reinforcement. However, the results show that the composites with composition of 1:3 weight ratio RHA:SiC (25% RHA: 75% SiC) offers comparable specific strength values with the single SiC reinforced Al composite grades. The strain to fractures was invariant to the weight ratio of RHA/SiC for all weight percent but the composite compositions containing RHA had improved fracture toughness compared with the single SiC reinforced Al composite grades.