Fabrication And Characterisation Of Aa7075 GR SIC FA Hybrid MMC And Its Application In Friction Stir Welding

Abstract

Metal matrix composites (MMCs) have become an unconquerable alternative to most conventional metals, attaining a broad appreciation in numerous technological areas owing to their worthier mechanical and thermal properties over traditional metals and alloys. A hybrid composite is a composite fabricated with more than one reinforcement. These hybrid metal matrix composites (HMMCs) were proven superior to single reinforced MMCs in many research works, with favourable enhancements in mechanical characteristics. The objective of the present work is to study the mechanical behaviour of the AA7075 composites, which comprises of processing of aluminium alloy composites from a high strength alloy of 7-Series (AA7075). These composites are prepared through the most economical and efficient route of liquid metallurgy technique, where AA7075 alloy has been reinforced with different weight percentages of three distinct elements, namely, Fly Ash (FA), Silicon Carbide (SiC) and Graphite (Gr), respectively, in a uniformly increasing manner. This began with adding 2% wt. of each reinforcement in the particulate form to AA7075 alloy and gradually enhanced by 1% wt for the rest of other compositions. Three different composites, of total % wt of each reinforcement in the order of 2%wt, 3%wt and 4%wt, were made and were titled AMMC1, AMMC2 and AMMC3, respectively. A pure AA7075 sample is also cast as the basis and titled as AMMCP. The liquid metallurgy process produces MMCs with a uniform dispersion of reinforcements to a greater extent, which is revealed through the microstructure analysis. Mechanical characterizations of these composites were conducted as per the standards of ASTM, covering tensile strength, hardness, compression and impact strength analysis. The evaluation of tensile strength capabilities has revealed that the ultimate tensile strength of the composites increased with the increase in percentage weight of each reinforcement, and their values were found better than the ultimate strength of the pure AA7075 casting. T