Influence of SiO2 form the rice husk ash and coal fly ash particles on the mechanical behaviour and grain characteristics of the stir-casted hybrid composites

Abstract

The grain characteristics and mechanical properties of aluminium composites reinforced with Rice Husk Ash (RHA) and Coal Fly Ash (CFA), produced by double stir casting in a sand mould, were investigated. As-cast Al.6063 alloys contained eutectic silicon with sharp, long elongated laths which reduces strength and limits their applications. Cold rolling operation was selected to break those eutectic laths and refine the grains for the purpose of property enhancement. RHA and CFA were chosen because they are economical, possess low density and are available in enormous quantities as solid waste by-products. They contain a substantial concentration of SiO2 and serve as a viable reinforcement for improving mechanical properties of aluminium composites. The reinforcements were added in varying concentrations (1.5 and 3.0 wt.%). Six specimens were fabricated of which five were cold-rolled. Image J and Origin software was used in evaluating the average grain size of the fabricated alloys and its composites. The results were discussed with the help of grain size distribution and profile plots. Structural and composition analysis were done using scanning electron microscopy (SEM), EDX and XRD. Hardness and tensile tests were conducted on the aluminium composites. The results indicated that Al.6063-3 wt.% CFA composite demonstrated the best balance of mechanical properties with hardness of 79 HV, tensile strength of 151 MPa and average grain size of 11.39 µm. This improvement is linked to the effect of SiO2 in CFA and plastic deformation of the specimens.