Effect of Coconut Shell Ash and Graphite Particles on Microstructure and Mechanical Properties of Recycled Aluminium Composites

Abstract

The current high demand for aluminium (Al) matrix composites with improved physical and mechanical properties has resulted in growing concern in the production of hybrid composites of aluminium at a lower cost. In the present work, an effort has been made to develop a hybrid aluminium matrix composite from waste aluminium cans, coconut shell ash (150 µm) and graphite (150 µm) particles by stir casting method. Composites were prepared by reinforcing recycled aluminium alloy with a combination of 0,2,4,6,8 % weight (wt.) fraction of coconut shell ash (CSA) and constant 2 % wt. the fraction of graphite. The cast produced were machined in accordance with ASTM standard into an appropriate coupon for microstructural examination, density measurement, tensile, impact and hardness tests. The micrograph showed reasonably uniform distribution of CSA and graphite particles in the matrix of aluminium alloy. Casting defects such as shrinkage did not manifest and porosity are minimal. The results also revealed a reduction in density and impact energy within the range of 2.46-2.23 g/cm3 and 12.92-4.76 J respectively. Hardness and tensile strength increased within the range of 220.9-266.4 HV and 27-57 MPa respectively. The result reveals that, the overall reduction of density and impact strength together with improved hardness and ultimate tensile strength of the composites. The control sample confirmed the retention of the reinforcements in the aluminium matrix. This study has affirmed the suitability of recycled aluminium cans reinforced with graphite and coconut shell ash as a candidate material for the production of the most common automobile part.