Enhanced mechanical behaviour and grain characteristics of aluminium matrix composites by cold rolling and reinforcement addition (Rice husk ash and Coal fly ash)

Aluminium matrix composites significantly benefit the manufacturing sector due to the high strength-to-weight ratio. However, grain refinement was one of the major problems faced by the research community and also as-cast AA6063 contained eutectic silicon with sharp, long elongated laths that consequently reduces strength and limit their applications. So, the prime novelty of this research work is to refine the grains by performing the cold rolling operation in AA6063 and incorporating rice husk ash and coal fly ash in the AA6063 matrix to break those eutectic laths which attributes to the enhancement of the mechanical properties. Rice husk ash and coal fly ash 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 the mechanical properties of aluminium composites. In this research, the grain characteristics along with the mechanical properties of aluminium composites reinforced with rice husk ash and coal fly ash, produced by the stir casting technique were investigated. 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 their composites. The results were discussed with the help of grain size distribution and profile plots. Structural and composition studies were done using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction spectroscopy. Hardness and tensile tests were performed on the fabricated composites. The outcome of this research reveals, AA6063-3 wt.% rice husk ash composite has improved hardness (84HV) and tensile strength (156 MPa). Moreover, the average grain size of 10.52 µm was the main reason for the attainment of enhanced mechanical properties.