Investigation of Microstructure and Several Quality Characteristics of AA7075/Al 2 O 3 /Coconut Shell Ash Hybrid Nano Composite Prepared through Ultrasonic Assisted Stir-Casting

The present study focuses on the investigation of mechanical, thermal, and corrosion behaviors of cast hybrid nano-metal matrix composites of AA7075 with Al 2 O 3 and coconut shell ash (CSA) nano- and micro-sized particulates, respectively, as reinforcements. Using an ultrasonic assisted stir-casting technique, the hybrid composites were fabricated using 2, 4, and 6% by weight of CSA and 0.5% by weight of Al 2 O 3 in equal proportions. SEM, EDS, XRD, porosity, tensile, damping, dislocation density, coefficient of thermal expansion, and polarization tests were used to characterize four different combinations. The findings indicated that the nano- and micro-sized particulates were spread evenly in the matrix. The dislocation density, which is caused by a thermal mismatch between the matrix and the reinforced particles, as well as composite porosity, have been found to have a significant impact on the damping behaviors of hybrid composites. Also, the thermal expansion coefficient of HMMCs decreased with the addition of Al 2 O 3 and CSA. The corrosion resistance was gradually increased by increasing the weight percentage of reinforcement in the AA7075 matrix.