Microstructural and mechanical characterization of novel AA7075 composites reinforced with rice husk ash and carbonized eggshells

This paper investigates microstructural and mechanical characteristics of novel AA7075 composites supplemented with agricultural waste, i.e. rice husk ash and poultry waste, i.e. carbonized eggshells. Both these wastes possess important constituents which make them potential reinforcement material for composites, and their utilization also reduces the problem of disposal to a certain extent. AA7075 composites with varying weight percentages of rice husk ash and carbonized eggshells were prepared through stir casting route. The sum of weight percentages of both reinforcements was kept constant at 5 wt.%. Composites were tested for density and different mechanical properties. Prior to these tests, composites were examined through scanning electron microscopy and energy-dispersive X-ray spectroscopy techniques, wherein uniform distribution of reinforcements was observed. Inclusion of light weight reinforcements decreased the density of composites. Among these composites, highest hardness value was shown by composite having 5 wt.% of rice husk ash with 24.47% enhancement over unreinforced AA7075. Maximum tensile strength and compression strength were exhibited by hybrid composite with 3.75 wt.% rice husk ash and 1.25 wt.% carbonized eggshells. This increment is 28.20% and 16%, respectively, over base composition. Impact strength decreased as the weight percentage of CES increased, thereby indicating brittleness in behaviour. Fractography analysis of tensile and impact test specimens was done through scanning electron microscopy to determine failure mode wherein presence of cracks, voids, dimples, debonding, etc. was observed. Hence, these light weight and low cost green AA7075 composites showed improved properties making them as an alternative as well as sustainable material for automotive and aerospace applications.