Abstract
Aluminium-based hybrid metal grid composites (MMC) are extensively utilized in automobile applications (engine cylinders, pistons, etc.) as they exhibit a fantastic blend of properties. Here, a detailed study of nano-mechanical, electrochemical and Raman spectroscopic behavior of friction stir processed Al6061-SiC-graphite hybrid surface composite is presented. The effect of various tool rotational speeds was evaluated along with the monitoring of variation in axial force. Microstructural changes with various tool rotational speeds are studied by using a scanning electron microscope. Raman spectroscopy and X-Ray diffraction studies are used for the spectroscopic characterization of the fabricated hybrid and mono surface composites. Residual stresses and various crystal structure disorders of reinforcement result in the significant change in intensity and a considerable shift in Raman peak positions. The nano-mechanical behavior of the fabricated composite with various reinforcements and tool rotational speeds are analyzed by using nano-indentation. The nano-mechanical behavior of hybrid composite fabricated with an optimum set of processing parameters is superior to mono composites fabricated with the same processing parameters. Also, the electrochemical behavior of the fabricated composites is studied by linear potentiodynamic polarization test. The Al6061-SiC-graphite hybrid surface composite reveals excellent nano-mechanical and electrochemical behavior when fabricated with an optimum set of processing parameters. The tool rotational speed has a pronounced effect on the dispersion of agglomerates and grain refinement of the matrix material. The processing parameters extensively affect the Raman spectroscopic behavior of the hybrid composite. The hybrid surface composite shows better corrosion resistance than the mono composites when fabricated with an optimum set of processing parameters. Reduced intergranular as well as interfacial corrosion pits in hybrid composites increased its resistance to corrosion.
Highlights
Aluminum-based hybrid metal grid composites (MMC) are widely utilized in automobile applications as they exhibit high strength, wear resistance, abrasion resistance, chemical stability, and dimensional stability at high temperature [1,2]
Friction stir processing (FSP) was first established by Mishra et al to impart high strain rate superplasticity to 7075 aluminum alloy [3]
Saxena et al [28] have shown in their work that graphite reinforcement leads to higher corrosion loss than the base alloy and aluminum due to the cathodic behavior of graphite particles relative to a matrix, which leads to increased rate of galvanic corrosion
Summary
Aluminum-based hybrid metal grid composites (MMC) are widely utilized in automobile applications (engine cylinders, pistons, etc.) as they exhibit high strength, wear resistance, abrasion resistance, chemical stability, and dimensional stability at high temperature [1,2]. Graphite reinforcement in Al matrix decreases the hardness, friction coefficient and coefficient of thermal expansion [24] while wear resistance increases considerably in comparison to the un-reinforced Al alloy [17,23,25,26]. The graphite provides a solid layer of lubricant between the composite and counter hard surface [27] This graphite layer helps to increase the wear resistance of the composite. Saxena et al [28] have shown in their work that graphite reinforcement leads to higher corrosion loss than the base alloy and aluminum due to the cathodic behavior of graphite particles relative to a matrix, which leads to increased rate of galvanic corrosion. It was reported in many works that the hybrid composite of Al-SiC-graphite exhibits better wear resistance than those reinforced only with SiC or graphite [30,31]. The spectroscopic analysis is to be conducted to study the morphological change of graphite due to the presence of SiC reinforcement in the hybrid composite
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