The unique physical and mechanical properties of metal matrix composites (MMCs) have attracted much research interest due to their wide use in the aerospace, marine, and automotive industries. Many recent studies have highlighted variations in the development of new composites with improved properties.
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MMCs are synthesized by integrating the two major constituents that comprise the hypo-eutectic blend of a metal alloy and the reinforcements. Aluminum matrix composites (AMC) are the most common type of MMCs. They combine different proportions of aluminum-silicon compounds, mainly silicon carbide (SiC) or alumina (Al2O3). The primary component is usually the reinforcing material dispersed in the matrix component of the secondary material, and this reaction occurs at the nano or molecular level.
The result is the formation of new electron orbits due to orbital interactions between the composite materials, leading to entirely new materials with properties not initially seen in the individual parent component. Various preparation processes include infiltration methods, stir casting, and sintering (powder metallurgy).
Examining aluminum composites at high temperatures is vital for developing airframes and wing structures for high-temperature applications. The heat treatment effect results in the production of AMCs with improved properties in terms of corrosion resistance, castability, high thermal conductivity, increased strength at high temperatures, low density, increased wear resistance, and high strength characteristics. This article explores current heat treatment approaches and their effects on the properties of aluminum hybrid composites.
Heat Treatment of Aluminum Composites
In a study in the journal Materials Science Forum, the mechanical properties of SiC/Gr reinforced hybrid aluminum composites were investigated after heat treatment. The composite consists of an Al-Mg-Si matrix alloyed with Zn. The reinforcement matrix consists of 5% Gr and 5% SiC, and the mechanical properties were examined in a heat treatment process that involves three stages - solution treatment, quenching, and artificial aging.
By varying the temperature at 140 oC, 180 oC, and 200 oC, the aging process was conducted and held for 2, 4, and 6 hours. Before the commencement of the treatment process, the authors reported that the reinforcement procedure involves melting the AMC in a crucible at 850 oC followed by adding the SiC/Gr particles in proportions of 5%. Optimization of the mixing composites was conducted by stirring at 7500 rpm and pouring them into a preheated mold at 300 oC.
The authors concluded that the heat treatment process affected the mechanical properties of the AMC. However, the highest hardness value of 60.3 HRA was reported at 200 oC after a heat treatment process that lasted for 6 hours, prompting the need for optimization in the aging processes to achieve the best result.
Recent Studies and Developments
In a study in the journal SN Applied Sciences, A356 aluminum alloy-based hybrid composites were reinforced using mica and TiO2 particles by the stir casting method. The reinforcements were used in equal proportions at varying concentration levels, and the corrosion resistance levels of the hybrid composites were investigated to determine the influence of heat treatment. Single aging was carried out at 140 oC for 12 hours, with two double aging procedures at 190 oC for 2hours and 190 oC for 4 hours, respectively.
The corrosion resistance test involved dipping the aluminum hybrid composites in a solution containing 5% NaCl, Sea Water, and 0.1N HCl solution for 96 hours. The authors reported an improvement in the corrosion resistance levels of the composites upon heat treatment. However, the sample subjected to double aging for 4 hours showed the highest resistance.
In another study in the journal Materials, the authors studied the tensile properties of aluminum AA 5083-SiC-fly ash composites to understand the effects of thermal exposure and reinforcements. Upon varying the concentrations (wt.%) of the reinforcement materials, the specimens were fabricated by subjecting them to heat treatment in line with the T6 thermal cycle to enhance their properties. After a series of scientifically designed trials, the authors reported an increase in the composites' yield strength and tensile strength up to 160 oC.
Further investigations revealed a slight reduction of the same parameters at 200 oC. The authors concluded that the observed improvements in the elastic modulus and tensile properties of the composites can be attributed to the composition of the reinforcements, the diffusion mechanism, grain refinement, and heat treatment temperature.
In engineering, composite materials play significant roles and have been used in the marine, aerospace, and automobile industries. The addition of various types of materials like SiC and graphite to form aluminum hybrid composites has been explored to investigate further and improve its physical and mechanical properties.
Furthermore, heat treatment as a process of improving these properties has been studied, and the outcomes documented. Higher heat treatment shows significant improvements depending on the material used in the reinforcement, although some studies reveal a decline at certain temperatures and exposure time. Although there is a need for additional studies, especially in optimization and material preference, there is no doubt that heat treatment is an essential factor in fabricating and influencing the properties of aluminum hybrid composites.
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References and Further Readings
Nagaraja, S., Kodandappa, R., Ansari, K., Kuruniyan, M. S., Afzal, A., Kaladgi, A. R., Aslfattahi, N., Saleel, C. A., Gowda, A. C., & Bindiganavile Anand, P. (2021). Influence of Heat Treatment and Reinforcements on Tensile Characteristics of Aluminium AA 5083/Silicon Carbide/Fly Ash Composites. Materials, 14(18), 5261. https://www.mdpi.com/1996-1944/14/18/5261
Rahmalina, D., Sukma, H., Abdul, R. and Suhadi, A. (2021). Mechanical Properties of SiC/Gr Reinforced Hybrid Aluminum Composites after Heat Treatment. Material Science Forum, vol. 1042, pp-111-115. https://teknik.univpancasila.ac.id/dosen/jurnal/Dwi%20Rahmalina%20Paten/2_Material%20Science%20Forum.pdf
Veeranaath, V., Daga, U., Sharma, P. and Kumar, Y. (2022). Analysis of the upshot of heat treatment on physical and mechanical behavior of aluminum hybrid composites. Materials Today: Proceedings, available online. https://www.sciencedirect.com/science/article/pii/S2214785322033491
Pinto, J. W., Sujaykumar, G., and Sushiledra, R. M. (2016). Effect of Heat Treatment on Mechanical and Wear Characterization of Coconut Shell Ash and E-glass Fiber Reinforced Aluminum Hybrid Composites. Americal Journal of Material Sciences, 6(4A): pp. 15-19. DOI:10.5923/c.materials.201601.03 http://article.sapub.org/10.5923.c.materials.201601.03.html
Prajval, S. and Prasad, R. P. (2019). Influence of heat treatment on the corrosion rate of aluminum A356 reinforced with mica and titanium dioxide. SN Applied Sciences, 1(1651). https://link.springer.com/article/10.1007/s42452-019-1686-7