Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Article Citation - WoS: 16Citation - Scopus: 17Investigation of the High Temperature Dry Sliding Wear Behavior of Graphene Nanoplatelets Reinforced Aluminum Matrix Composites(SAGE Publications, 2021) Martin, Seçkin; Kandemir, Sinan; Antonov, M.In this study, graphene nanoplatelets (GNPs) with a thickness of 50-100 nm have been utilized to improve the mechanical and tribological properties of A360 alloy due to their extraordinary mechanical properties and solid lubricant nature. For the investigation of tribological properties, ball-on disc tests were carried out at various temperatures including room temperature (RT), 150 °C, and 300 °C. According to the hardness and ball-on-disc test results, the nanocomposite samples reinforced with GNPs exhibited improved hardness and wear resistance. The improvement in the wear behavior of nanocomposites was referred to the temporarily formed solid lubricant film of harder GNPs during the wear, and hence coefficient of friction (COF) and volume loss were considerably reduced. Abrasive-adhesive, oxidative, and mild-to-severe were found to be main wear mechanisms at RT, 150 °C, and 300 °C, respectively. Overall, the results show that the nanocomposites fabricated by casting method combined with mechanical stirring and ultrasonication have promising wear performance, especially at elevated temperatures. This may suggest that these developed materials could be potential candidates to be used in the engineering applications requiring high temperature wear performance. © The Author(s) 2020.Article Citation - WoS: 35Citation - Scopus: 39Development of Graphene Nanoplatelet-Reinforced Az91 Magnesium Alloy by Solidification Processing(Springer Verlag, 2018) Kandemir, SinanIt is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites.