WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 13Citation - Scopus: 16Influence of Recycled Carbon Fiber Addition on the Microstructure and Creep Response of Extruded Az91 Magnesium Alloy(KeAi Communications Co., 2023) Kandemir, Sinan; Bohlen, Jan; Dieringa, HajoIn this study, the recycled short carbon fiber (CF)-reinforced magnesium matrix composites were fabricated using a combination of stir casting and hot extrusion. The objective was to investigate the impact of CF content (2.5 and 5.0 wt.%) and fiber length (100 and 500 µm) on the microstructure, mechanical properties, and creep behavior of AZ91 alloy matrix. The microstructural analysis revealed that the CFs aligned in the extrusion direction resulted in grain and intermetallic refinement within the alloy. In comparison to the unreinforced AZ91 alloy, the composites with 2.5 wt.% CF exhibited an increase in hardness by 16–20% and yield strength by 5–15%, depending on the fiber length, while experiencing a reduction in ductility. When the reinforcement content was increased from 2.5 to 5.0 wt.%, strength values exhibited fluctuations and decline, accompanied by decreased ductility. These divergent outcomes were discussed in relation to fiber length, clustering tendency due to higher reinforcement content, and the presence of interfacial products with micro-cracks at the CF-matrix interface. Tensile creep tests indicated that CFs did not enhance the creep resistance of extruded AZ91 alloy, suggesting that grain boundary sliding is likely the dominant deformation mechanism during creep. © 2023Article Citation - WoS: 6Citation - Scopus: 6Tribocorrosion-Resistant Ti40nb-Tin Composites Havingtio(2)-Based Nanotubular Surfaces(American Chemical Society, 2022) Çaha, İhsan; Alves, Alexandra Cruz; Chirico, Caterina; Pinto, Ana Maria; Tsipas, Sophia; Gordo, Elena; Toptan, FatihA novel multifunctional material was developed byhard TiN particle reinforcement addition to a beta-type Ti40Nb alloy,followed by surface functionalization, yielding the formation of ananotubular layer. Corrosion and tribocorrosion behaviors wereinvestigated in a phosphate-buffered saline solution at bodytemperature. The results revealed that the Ti40Nb-TiNcomposites presented similaripassandE(i=0)values together withrelatively similarRoxandCox. However, its tribocorrosion resistancedrastically improved (wear volume is almost 15 times lower than anunreinforced alloy) as a consequence of the load-carrying effectgiven by the reinforcement phases. The corrosion and tribocorro-sion behaviors were further improved through surface functionaliza-tion as observed by significantly loweripassand higherRoxvalues andalmost undetectable wear volume loss from tribocorrosion tests dueto the formation of a well-adhered anatase-rutile TiO2-based nanotubular layer.Article Citation - WoS: 22Citation - Scopus: 27Improved Tribocorrosion Behavior on Bio-Functionalized Β-Type Titanium Alloy by the Pillar Effect Given by Tin Reinforcements(Elsevier, 2021) Çaha, İhsan; Alves, Alexandra C.; Chirico, Caterina; Pinto, Ana Maria; Tsipas, Sophia; Gordo, Elena; Toptan, FatihA novel multi-functional material was developed by hard TiN particle reinforcement addition to a beta-type Ti alloy, following by bio-functionalization of its surface through Ca and P rich oxide layer. Corrosion and tribocorrosion behavior of this multi-functional material was investigated in phosphate buffer solution at body temperature. Bio-functionalization drastically improved the corrosion and tribocorrosion behavior of the unreinforced and reinforced samples, where the bio-functionalized beta-type titanium alloy matrix composite presented the best tribocorrosion behavior due to the load-carrying role of the hard reinforcement phase that gave a support to the functionalized surface layer.Article Citation - WoS: 41Citation - Scopus: 45High Temperature Tensile, Compression and Creep Behavior of Recycled Short Carbon Fibre Reinforced Az91 Magnesium Alloy Fabricated by a High Shearing Dispersion Technique(National Engineering Research Center for Magnesium Alloys of China, Chongqing University, 2021) Kandemir, Sinan; Gavras, Sarkis; Dieringa, HajoThe present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys. The microstructures, high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents (2.5 and 5 wt.%) and lengths (100 and 500 ?m) were investigated in the temperature range of 25–200 °C. The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres. The materials tested displayed different behaviour depending on the type of loading. In general, while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres, the fluctuations in the properties were discussed on the basis of porosity formation, relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy. The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91. © 2021Article 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.Article Citation - WoS: 9Citation - Scopus: 9Quasi-Static and High Strain Rate Properties of a Cross-Ply Metal Matrix Composite(Elsevier Ltd., 2009) Hall, Ian W.; Taşdemirci, Alper; Derrick, J.A series of compression tests has been carried out at quasi-static and high strain rates on cylindrical samples of an alumina fiber/Al-6061 metal matrix composite. The composite plates were prepared with fibers in the 0°, 0/90° and ±45° orientations. It was found that the mechanical properties were strongly dependent upon the imposed strain rate, with fracture stress increases of >50% being noted for several orientations at high strain rates: these increases are not believed to be related to strain rate sensitivity of either the matrix or fibers but to arise from the inertia of fragments which remain in place after fracture and continue to bear load. Also, and in contradiction to behavior anticipated from the rule of mixtures, it was found that 0/90° samples exhibited properties superior to those of 0° unidirectional samples. High-speed photography was used to confirm the sequence of deformation and fracture events at high strain rate. © 2008 Elsevier B.V. All rights reserved.Article Citation - WoS: 41Citation - Scopus: 38Simulation of the Strain Rate Sensitive Flow Behavior of Sic-Particulate Reinforced Aluminum Metal Matrix Composites(Elsevier Ltd., 2008) Tirtom, İsmail; Güden, Mustafa; Yıldız, HasanStrain rate dependent compression mechanical behavior of an SiC-particulate reinforced Al (2024-O) metal matrix composite (MMC) with different particle volume fractions was numerically investigated at various strain rates. Calculations were performed using axisymmetric finite element unit cell model, in which an elastic SiC particle was embedded inside a strain rate sensitive viscoplastic Al matrix. Stress–strain curves of Al matrix material were derived from Split Hopkinson Pressure Bar experiments at various strain rates and used as inputs in the FEM model. Numerically computed stress–strain curves and strain rate sensitivity were compared with those of experiments for a 15% SiC-particulate reinforced MMC. Computed strain rate sensitivity of the MMC was found to be higher than that of the matrix alloy and increased with increasing strain contrary to the strain independent matrix strain rate sensitivity. The strain rate sensitivity of the MMC was also found to increase with increasing particle volume fraction at the same particle size. Finally, several possible reasons including assumptions used in the model, adiabatic heating, microstructural variations between the composite matrix and matrix alloy, particle shape and distribution and damage accumulation for the small discrepancy found between computed and experimental stress–strain curves and strain rate sensitivity of the composite were discussed.Article Citation - WoS: 11Citation - Scopus: 14Quasi-Static and Dynamic Compression Behaviour of an Fptm Alumina-Reinforced Aluminium Metal Matrix Composite(Springer Verlag, 1998) Güden, Mustafa; Hall, Ian W.An aluminium metal matrix composite reinforced with continuous unidirectional α-alumina fibres has been compression tested at quasi-static and dynamic strain rates. In the transverse direction, the composite showed increasing flow stress (at 5% strain) and maximum stress within the studied strain rates, 10−3−3 × 103 s−1. In the longitudinal direction, the maximum stress of the composite increased similarly with increasing strain rates within the range 10−5−7 × 102 s−1. It is shown that, if brooming of the sample ends can be suppressed, the failure stress of the composite in longitudinal compression increases significantly. Metallographic observations reveal the typical modes of damage initiation in the composite.Article Citation - WoS: 37High Strain-Rate Compression Testing of a Short-Fiber Reinforced Aluminum Composite(Elsevier Ltd., 1997) Güden, Mustafa; Hall, Ian W.Compression behavior of 15–26 Vf% Saffil™ short-fiber reinforced Al-1.17wt.%Cu alloy metal matrix composites has been determined over a strain-rate range of approximately 10−4 to 2×103 s−1. The strain-rate sensitivity of composite samples at 4% strain, tested parallel and normal to the plane of reinforcement, was found to be higher than that of unreinforced alloy in the strain-rate range studied. Quantitative analysis of fiber fragment lengths from samples tested to different strain levels showed that, at small strains, high strain-rate testing induced a relatively shorter fiber fragment length distribution in the composite compared to quasi-static testing. At quasi-static strain rates, the fiber strengthening effect was found to increase with increasing Vf% and was higher in samples tested parallel to the planar random array. The observed anisotropy of the composite at quasi-static strain rates was also observed to continue into the high strain-rate regime. Microscopic observations on composite samples tested quasi-statically and dynamically to a range of strains showed that the major damage process involved during compression testing was fiber breakage followed by the microcracking of the matrix at relatively large strains. Fiber breakage modes were found to be mostly shearing and buckling.Article Citation - WoS: 44Dynamic Properties of Metal Matrix Composites: a Comparative Study(Elsevier Ltd., 1998) Güden, Mustafa; Hall, Ian W.Three distinctly different metal matrix composites have been tested at strain rates from quasi-static to ≈3000 s−1. It was found that the high strain rate response of each composite was determined primarily by (a) the response of the matrix in the absence of any reinforcement and (b) the damage formation and accumulation processes during deformation. High strain rate behavior of the short fiber composite was dominated by the matrix behavior at low strains but by fiber damage at high strains. The behavior of a whisker reinforced composite was dominated by the matrix properties at all strains. Re-loading tests produced increased fracture strains, indicating that adiabatic heating accelerates fracture of composites by permitting the development of local strain instabilities.