STUDY OF MECHANICAL AND TRIBOLOGICAL BEHAVIOUR OF AL BASED HYBRID MMCS FABRICATED BY STIR CASTING PROCESS

Abstract

Micro/nano reinforcements in aluminium matrix composites (AMCs) have recently gained attention for a number of applications due to their lightweight and better mechanical, tribological, thermal, and electrical properties. The incorporation of industrial and agricultural waste materials as reinforcements for the production of metal matrix composites (MMCs) is the utilization of waste and a reduction of pollution. A number of industries, including aerospace, automotive, and packaging, have demonstrated a keen interest in the development of innovative bio-waste particulate reinforced composite. The effect of reinforcements is investigated in the current research work. The two-stage stir casting method with Al203 and coconut shell ash (CSA) is reinforced with an aluminium matrix. Two sets of hybrid composites have been developed using i) nano Al203, ii) micro Al203 and iii) coconut shell ash as reinforce material and AA7075 as the matrix. The first hybrid composites contain 0.5% w/w of nano Al203 as reinforce material with varied 1-3% w/w of micro coconut shell ash in the AA7075 matrix. Second hybrid composites contain 5% w/w of micro Al203 with varied 3-9% w/w of micro coconut shell ash as reinforcements in AA7075 matrix. The present study focuses on the investigation of mechanical, thermal, and wear behaviors of cast hybrid nano metal matrix composites (HnMMCs) of AA7075 with Al203 and coconut shell ash (CSA) nano and micro-sized particulates, respectively, as reinforcements. Microstructural analysis and various phase identifications were examined with the help of an optical microscope (OM), scanning electron microscope (SEM) equipped with EDX and Transmission electron microscope (TEM). Due to the two-stage stir casting process, the distribution of reinforcement in the aluminium matrix is ensured to be uniform. It was discovered that the addition of Al203 and CSA reinforced particles improved mechanical characteristics and tribological behaviour while decreasing impact strength marginally. SEM images of fractured specimens during impact and tensile testing revealed transgranular cleavage facets, micro-void coalescence, dimples, and a crack. The

tribological characteristics of the worn-out surfaces were examined extensively using SEM images. Overall, employing CSA in combination with Al203 in HMMCs may be an effective, smooth, and cleaner method for disposing of Al203 in terms of environmental pollution and waste contamination due to large-scale application in improving composite characteristics.