Investigation of Nano-Al₂O₃ and Micro-coconut Shell Ash (CSA) Reinforced AA7075 Hybrid Metal–Matrix Composite Using Two-Stage Stir Casting

The present work is focused on the influences of reinforced particles on mechanical, microstructural, and tribological performances of AA7075 hybrid metal–matrix composites (HMMCs). Al₂O₃ and coconut shell ash (CSA) were reinforced using two-stage stir casting by varying the wt% (0–5) of reinforcement. Microstructural analysis and various phase identifications were examined with the help of scanning electron microscope (SEM) equipped with EDX and optical microscope. Various mechanical testing such as tensile, hardness, 3-point bend test, and tribological behaviors were carried out to know the HMMCs properties. Microstructural images revealed a homogeneous distribution of reinforced particles in the metal–matrix and EDX confirmed the presence of dispersed reinforcements (Al₂O₃ and CSA) in the HMMCs. It was seen that mechanical properties and tribological behavior have been increased after addition of Al₂O₃ and CSA reinforced particles whereas slightly decreased in impact strength. Transgranular cleavage facets, micro-void coalescence, dimples, and crack were shown in SEM images of fractured specimens during impact and tensile testing.