Investigative Study of the Structure and Mechanical Behaviour of Horse Eye Bean Seed Shell Ash Reinforced Aluminium Alloy Matrix Composite

Abstract

This research investigated the structure and mechanical behaviour of horse eye bean seed shell ash reinforced aluminium alloy matrix composite. The horse eye bean seed shell ash of particle sizes (300 and 500?m) was added in concentrations of 5 and 15% by weight. The composite was developed using permanent die casting technique and machined to the required dimensions for tensile strength, hardness and impact strength. The machined samples were subjected to heat treatment at 410oC for 30 minutes, quenched in water and aged at temperatures of 100 and 300oC for 2 and 6hrs. Mechanical properties such as percentage elongation, ultimate tensile strength, Brinell hardness and impact strength were determined using a 100KN JPL tensile strength tester (Model: 130812), portable dynamic hardness testing machine (Model: DHT-6) and pendulum impact testing machine (Model: U1820) respectively. The structural analysis was conducted using an optical metallurgical microscope (Model: L2003A), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffractometer (XRD). The microstructure of the control sample revealed the presence of polyhedral-shaped primary silicon particles and needle-like precipitate of intermetallic compound. The composite showed fine intermetallic phases dispersed in the aluminium matrix. The result of the mechanical tests indicated that addition of horse eye bean seed shell ash significantly improved the ultimate tensile strength, hardness and impact strength of the aluminium alloy matrix. The ultimate tensile strength and hardness increased with decrease in reinforcement particle size and increase in percentage by weight of reinforcement and ageing temperature. Maximum ultimate tensile strength was obtained by the composite containing 5% by weight of reinforcement (500?m), aged at 300oC for 2 hrs. This was attributed to the fine intermetallic phases dispersed in the aluminium matrix. Maximum hardness was obtained by the composite containing 5% by weight of reinforcement (300?m), aged at 100oC for 2 hrs. This was linked with the presence of Al0.64Ti0.36, Al12Mg17, C0.12 Fe0.79 Si0.09, MgAl2O4, TiC, FeSi, SiC and AlMg evenly distributed in the aluminium matrix. Optimum impact strength was obtained by the composite containing 15% by weight of reinforcement (500?m) and aged at 100oC for 2 hrs.