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Öğe Al-Si-Cu-Mg Matrix Composites with Graphene: PM-Based Production, Microstructural, and Mechanical Properties(Wiley-V C H Verlag Gmbh, 2024) Senyurt, Berk; Agaogullari, Duygu; Akcamli, NazliFew-layered graphene (FLG)-reinforced Al-Si(10 wt%)-Cu(2 wt%)-Mg(1 wt%) matrix composites are prepared by the high-energy mechanical alloying (MA) method, which is a branch of powder metallurgy. Al-10Si-2Cu-1Mg matrix is reinforced with varying amounts of FLG (0, 0.5, 1, 2, and 5 wt%) via MA for different durations (0, 2, 4, and 8 h), and consolidation is conducted by pressureless sintering. Microstructural, mechanical, and tribological characterizations are applied to nonmechanically alloyed (non-MAed) and mechanically alloyed (MAed) powder and bulk composites comparatively. The bulk composites produced via the MA-containing processing route illustrate more homogeneous phase distributions and higher densification rates. The FLG/AlSiCuMg composites exhibit enhanced materials properties compared to their unreinforced counterparts. The addition of 1 and 2 wt% FLG to the Al-10Si-2Cu-1Mg alloy, respectively, improved the mechanical properties in terms of microhardness (155 and 162 HV), compression strength (441 and 412 MPa), and wear rate (11.5 x 10-4 and 9.2 x 10-4 mm3 N-1 m). Therefore, the experimental results show that graphene ensures a reinforcing effect on the Al matrix, at least provided by some of the ceramic particles. This study explores the microstructural, tribological, and mechanical properties of few-layered graphene (FLG)/Al-10Si-2Cu-1Mg composites produced by the powder metallurgy route, including a high-energy mechanical alloying (MA) stage. FLG is synthesized in-house by the arc-discharge method. The effects of MA processing duration along with various FLG amounts on the materials properties of the powder and bulk composites are investigated.image (c) 2024 WILEY-VCH GmbHÖğe Characterization of mechanically alloyed and pressureless sintered Al-7 wt% Si-2 wt% LaB6-2 wt% (MoSi2, WSi2) hybrid composites(Elsevier, 2019) Tekoglu, Emre; Yürektürk, Yakup; Agaogullari, Duygu; Ovali, Didem; Mertdinc, Siddika; Ovecoglu, M. LutfiThe purpose of this research is to investigate the dual effect of silicide (MoSi2 or WSi2) and LaB6 reinforcing particles on the microstructural and mechanical properties of Al-7 wt% Si (Al7Si) matrix. Hypoeutectic Al7Si blends prepared from elemental Al and Si powders were mechanically alloyed (MA'd) for 12 h in a planetary ball mill (at 300 rpm). Afterwards, 2 wt% silicide reinforcements (MoSi2 or WSi2) with various particle size distributions (micron, bimodal, submicron) were separately added into these MA'd Al7Si powders together with 2 wt% of LaB6 particles. Powders having compositions of Al7Si, Al7Si-2 wt% LaB6, Al7Si-2 wt% LaB6-2 wt% MoSi2 and Al7Si-2 wt% LaB6-2 wt% WSi2 were milled for 30 min using a high-energy ball mill (at 1200 rpm) in order to obtain homogeneous distribution throughout the microstructure. Compositional, microstructural and mechanical characterization studies were performed on the sintered samples. The results showed that high-energy ball milling ensured the homogeneous distribution of micron-sized MoSi2 and WSi2 particles within the matrix rather than those of bimodal and submicron-sized ones. Micron-sized MoSi2 and WSi2 reinforced hybrid composites displayed dramatically higher hardness and wear resistance than those of composites reinforced with different size of MoSi2 and WSi2 particles. The striking point of the study was the remarkably higher hardness and wear resistance properties of the hybrid composites compared to those of un-reinforced and only LaB6-reinforced ones. As a conclusion, hybrid composites extremely displayed promising mechanical properties. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.Öğe Effects of different milling conditions on the properties of lanthanum hexaboride nanoparticles and their sintered bodies(Elsevier Sci Ltd, 2019) Agaogullari, Duygu; Balci, Ozge; Akçamlı, Nazlı; Duman, Ismail; Ovecoglu, M. LutfiIn this study, the preparation and consolidation of nanocrystalline LaB6 powders originating from powder blends of La2O3, B2O3 and Mg were reported. A consecutive route of mechanochemical synthesis (MCS) and purification was utilized for the achievement of nano-sized LaB6 powders. As-synthesized powders were leached out from intermediate reaction products or impurities. Then, a sequential step of cold pressing (uniaxial pressure at 800 MPa) and pressureless sintering (at 1700 degrees C for 5 h under Ar gas flow) were utilized for the consolidation of the purified LaB6 powders. The type of mill (vibratory and planetary high-energy ball mills) was employed as a MCS parameter to reveal its effect on the physical, microstructural and mechanical properties of the LaB6 powders, and their bulk structures. Compositional, physical and microstructural properties of the products after powder processing were determined via X-ray diffractometer (XRD), particle size analyzer (PSA), differential scanning calorimeter (DSC), stereomicroscope (SM), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer (EDS) coupled with both SEM and TEM, and vibrating sample magnetometer (VSM). The bulk properties of the LaB6 consolidated from nanocrystalline powders with a minimum 99.99% purity, and similar to 62 nm (for vibratory ball mill) or similar to 74 nm (for planetary ball mill) average particle size were compared according to various properties. LaB6 powders were synthesized in planetary mill at an approximately six times longer duration than that of in vibratory mill. According to the results, density, surface area and mean particle size values of the vibratory ball-milled samples (containing paramagnetic powders) are better than those of planetary ball-milled (containing diamagnetic powders) ones. However, mechanical properties such as hardness, surface roughness, wear rate, friction coefficient, and also electrical conductivity were improved in the planetary ball-milled LaB6 bulks.Öğe In-situ synthesis of tungsten boride-carbide composite powders from WO3-B2O3-Mg-C quaternary system via a mechanochemical route(Elsevier Sci Ltd, 2021) Şenyurt, Berk; Akçamlı, Nazlı; Agaogullari, DuyguIn this study, in-situ synthesis of tungsten boride-carbide composite powders using a mechanochemical processing (MCP) method was investigated on the WO3-B2O3-Mg-C quaternary powder system. The raw blends of WO3-B2O3-Mg-C were processed in a high-energy ball mill for between 8 and 24 h. In addition to the MCP duration, excess B2O3 or C reactants and ball-to-powder weight ratio (BPR) were tested as important process parameters which affected the resultant phases. After the mechanochemical reaction, the products were purified using 6 M HCl solution to eliminate the MgO by-product. FactSage 7.1 and HSC Chemistry Ver.4.1 thermochemical software was used to predict the thermodynamically possible reactions and products. Microstructural properties of the fabricated powders were inspected through X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) and energy dispersive spectroscopy (EDS) techniques. Additionally, changes in particle size with duration of the MCP were determined for the synthesized powders. According to the XRD results, tungsten boride and tungsten carbide phases were obtained as the main reaction products for all reaction durations and reactant stoichiometries. Distribution of the total amounts of tungsten boride and tungsten carbide phases were determined respectively as 79.8 and 20.2 wt% for the 8 h-processed stoichiometric powders. However, the total tungsten boride amount decreased with the increasing MCP duration and its respective percentage was calculated as 57.1 wt% for the 24 h-processed stoichiometric powders. In addition, by increasing the processing duration to over 12 h, W2B, W2C and B4C phases were detected. When 200 wt% B2O3 was added, the B:W ratio and total amount of tungsten boride phases in the synthesized powders increased. Similarly, by utilizing 200 wt% C, a significant increase in the B4C peaks together with W2C peaks was detected. Therefore, the properties of tungsten boride-carbide composite powders synthesized by the mechanochemical route are highly affected by the process parameters.Öğe Investigation of indentation and dry sliding wear behaviour of Al-12.6 wt.% Si-10 wt.% TiB2 composites produced by sequential milling and pressureless sintering(Carl Hanser Verlag, 2019) Tekoglu, Emre; Yürektürk, Yakup; Agaogullari, Duygu; Dilawary, Shaikh Asad Ali; Baydogan, Murat; Ovecoglu, M. LutfiThe main purpose of this study is to comprehend the effects of cryomilling (CM) time on dry sliding wear behaviour of 10 wt.% TiB2 reinforced Al-12.6 wt.% Si metal matrix composites (MMCs). The MMCs were synthesised via sequential milling (mechanical alloying + cryomilling) and pressureless sintering. Indentation tests performed at a maximum load of 200 g showed that the Young's modulus and hardness of the composites increased up to 20 min of CM time. The effects of CM time and load on the composites were examined based on their tribological properties. Based on the results, the 4 h mechanical alloyed (MA'd) and 30 min CM'd sample showed the lowest wear rate under the normal load of 1 N, with its wear mechanism being predominantly oxidative. However, for the normal load of 4 N, the lowest wear rate was found in the 4 h MA'd composite, in which the dominant wear mechanism was abrasion.Öğe Investigation of the structural properties and corrosion behavior of few-layered graphene reinforced Al-Zn matrix P/M composites(Elsevier, 2025) Borand, Gokce; Senyurt, Berk; Agaogullari, Duygu; Uzunsoy, Deniz; Akcamli, NazliA powder metallurgical production route was employed to produce Al-7.5 wt% Zn matrix composites reinforced with few-layered graphene (FLG). The in-house synthesized FLG by the electric arc discharge (EAD) method was incorporated into the Al-7.5Zn matrix through mechanical alloying (MA) in varying amounts (0, 0.5, 1.0, and 2.0 wt%). The mechanically alloyed (MAed) powders were consolidated by uniaxial pressing, and they were subjected to pressureless sintering at 635 degrees C for 2 h. The effects of FLG contents (0, 0.5, 1, and 2 wt%) and MA duration (0, 2, 4, and 8 h) were investigated regarding the microstructural, mechanical, tribological, and corrosion properties of bulk composites. The hardness values of 4 h MAed FLG/Al-7.5Zn composites having graphene in amounts of 0, 0.5, 1, and 2 wt% were determined as 77, 89, 107, and 119 HV, respectively. Compared to Al-7.5Zn alloy, 2 wt% FLG addition significantly increased the hardness of 4 h MAed Al-7.5Zn composites by approximately 54 %. In line with the hardness results, the addition of FLG notably and gradually enhanced the wear resistance of the composites. The Al-7.5Zn matrix displayed an ultimate compressive strength (sigma ucs) of 180 MPa, which significantly rose to 287 MPa for the Al-7.5Zn-1FLG composite, indicating a 1.6-times enhancement. Moreover, the addition of this amount of graphene did not degrade the corrosion performance of the Al-Zn matrix; in fact, it resulted in a slight improvement in the corrosion resistance of the composites.Öğe Mechanochemical synthesis and consolidation of nanostructured cerium hexaboride(Univ Novi Sad, Fac Technology, 2019) Agaogullari, Duygu; Balci, Ozge; Akçamlı, Nazlı; Suryanarayana, Challapalli; Duman, Ismail; Ovecoglu, Mustafa LutfiThis study reports on the mechanochemical synthesis (MCS) and consolidation of nanostructured CeB6 powders of high purity. CeB6 powders were prepared via MCS by milling CeO2, B2O3 and Mg powders in a high-energy ball mill for different milling times. The effects of milling time on the formation, microstructure and thermal behaviour of the synthesized powders were investigated and the optimum MCS duration was determined. Purified powders were obtained after HCl leaching by removing MgO by-product. The prepared powders were characterized by a number of techniques including X-ray diffraction, stereomicroscopy, scanning and transmission electron microscopy coupled with energy dispersive spectrometry, differential scanning calorimetry, atomic absorption spectrometry, particle size analysis, surface area analysis and vibrating sample magnetometry. The high-purity CeB6 powders having an average particle size of 86 nm were consolidated by cold-pressing followed by pressureless sintering at 1700 degrees C for 5 h. The bulk CeB6 specimen was investigated for its microstructure, density, electrical resistivity, surface roughness and some mechanical properties (microhardness and wear behaviour). The relative density, electrical resistivity, microhardness and wear rate of the bulk CeB6 were determined as 95.2% TD, 57.50 mu W.cm, 11.65 GPa and 1.46 x 10(-4) mm(3)/N.m, respectively.Öğe Powder metallurgical fabrication of graphene reinforced near-eutectic Al-Si matrix composites: Microstructural, mechanical and electrochemical characterization(Elsevier - Division Reed Elsevier India Pvt Ltd, 2022) Akcamli, Nazli; Senyurt, Berk; Gokce, Hasan; Agaogullari, DuyguAl-10 wt% Si matrix composites reinforced with a few-layered graphene (FLG) were fabricated via a powder metallurgical route. FLG in varying amounts (0.25, 0.5, 1, 2, and 5 wt%) was incorporated into the Al10Si matrix via mechanical alloying (MA) for different durations in a high-energy ball mill. The mechanically alloyed (MAed) powders were consolidated by uniaxial pressing and pressureless sintering processes. The as-blended (non-MAed) and MAed powders and bulk composites were investigated comparatively in terms of microstructural, thermal, mechanical, tribological and corrosion properties. The MAed powders demonstrated refined and semi-equiaxed particle morphology with reduced crystallite size values. Additionally, the FLG/Al10Si composites exhibited advanced microstructural and mechanical properties by the contribution of MA and reinforcing particles compared to those of the as-blended and unreinforced matrix. The highest hardness and lowest wear rate values were obtained for the 4 h-MAed Al10Si-2FLG (138 HV and 6.485x10-4 mm(3)/N.m) and Al10Si-5FLG (178 HV and 7.456x10-4 mm(3)/N.m) composites. Moreover, the compressive strength of the Al-10Si matrix improved approximately by 50 and 20% via 0.5 and 2 wt% FLG addition, respectively. Also, lower corrosion resistance properties were observed for the FLG reinforced composites compared to the Al10Si matrix. (c) 2021 Karabuk University. Publishing services by Elsevier B.V.Öğe Solid-state synthesis of Cr2AlC MAX phase from mechanically activated Cr/ Al/C powder blends(Elsevier Science Sa, 2025) Senyurt, Berk; Agaogullari, Duygu; Akcamli, NazliThis study focuses on synthesizing the ternary-layered chromium aluminum carbide phase (Cr2AlC MAX) via a milling-assisted solid-state synthesis method. The elemental powders of Cr, Al, and C were processed in a twostage process following mechanical activation (MAc) and annealing. Various parameters in both stages (such as milling time, annealing temperature, and process control agent) were examined to optimize the production of a high-purity Cr2AlC MAX phase. For this purpose, the elemental powders underwent MAc through high-energy ball milling for 1, 3, and 5 h and annealing at temperatures ranging from 700 to 1500 degrees C. The formation mechanism of the Cr2AlC phase was discussed based on detailed characterizations, including differential thermal calorimetry (DSC), X-ray diffraction (XRD), and Rietveld analyses. Additionally, the morphological properties of the synthesized powders were investigated in detail via scanning and transmission electron microscopy (SEM and TEM) techniques. The initial formation of the MAX phase was observed at 700 degrees C, and it was completed with a meager amount of chromium carbide phase at higher temperatures (99.7 % Cr2AlC at 1100 degrees C) depending on the synthesis conditions. In addition, a single-phase Cr2AlC MAX without a carbide impurity was achieved with the addition of SA, which caused an increase in the annealing temperature to 1300 degrees C.Öğe Synthesis of bulk nanocrystalline HfB2 from HfCl4-NaBH4-Mg ternary system(Springer, 2017) Akçamlı, Nazlı; Agaogullari, Duygu; Balci, Ozge; Ovecoglu, M. Lutfi; Duman, IsmailThis study reports on the synthesis and consolidation of pure HfB2 powders starting from HfCl4-NaBH4-Mg blends via autoclave processing, annealing and purification followed by pressureless sintering (PS, with 2 wt% Co aid) or spark plasma sintering (SPS). During autoclave reactions conducted at 500 A degrees C for 12 h under autogenic pressure, excess amounts of NaBH4 were utilized to investigate its effects on the reaction products and mechanism. A subsequent washing (with distilled water), annealing (at 750, 1000 and 1700 A degrees C) and acid leaching (HCl) were applied on the as-synthesized products. Pure HfB2 powders with an average particle size of 145 nm were obtained after autoclave synthesis in the presence of 200 wt% excess NaBH4, washing, annealing at 1000 A degrees C for 3 h and 6 M HCl leaching. SPS sample has higher relative density and microhardness values (94.18% and 20.99 GPa, respectively) than those of PS sample (90.14% and 14.85 GPa). Relative wear resistance was improved considerably (8.2 times) by employing SPS technique.Öğe Synthesis of HfB2 powders by mechanically activated borothermal reduction of HfCl4(Elsevier Sci Ltd, 2016) Akçamlı, Nazlı; Agaogullari, Duygu; Balci, Ozge; Ovecoglu, M. Lutfi; Duman, IsmailHfB2 powders were synthesized via a borothermal reduction route from mechanically activated HfCl4 and B powder blends. Mechanical activation of the powder blends was carried out for 1 h in a high-energy ball mill using hardened steel vial and balls. Mechanically activated powders were subsequently annealed at 1100 degrees C for 1 h under Ar atmosphere. Then, purification processes such as washing with distilled water and leaching in HCl solution were applied for the elimination of the undesired boron oxide (B2O3) phase and the probable Fe impurity. The effect of boron amount on the microstructure of the resultant powders was investigated. The boron amount in the starting blends plays an important role in the formation of the HfO2 phase. HfB2 powders without any detectable HfO2 were prepared by adding 20 wt% excess amount of boron. Microstructural analyses of the mechanically activated, annealed and purified powders were performed using X-ray diffractometer (XRD), particle size analyzer (PSA), stereomicroscope (SM), scanning electron microscope/energy dispersive spectrometer (SEM/EDS) and transmission electron microscope (TEM). (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Öğe Synthesis of triclinic and hexagonal SmBO3 powders by mechanically activated annealing of Sm2O3 and B2O3 blends(Elsevier Sci Ltd, 2016) Akçamlı, Nazlı; Agaogullari, Duygu; Balci, Ozge; Ovecoglu, M. Lutfi; Duman, IsmailSamarium borate (SmBO3) powders were fabricated from oxide raw materials by a two-step solid-state synthesis method including mechanical activation and annealing. Blends containing stoichiometric amounts of samarium oxide (Sm2O3) and boron oxide (B2O3) were mechanically activated in a high-energy ball mill and subsequently annealed in air. Afterwards, mechanically activated and annealed powders were washed with distilled water in order to remove probable unreacted B2O3 phase. The effects of mechanical activation duration (15 min, 1 h, 3 h and 9 h) and annealing temperature (700-1250 degrees C) on the resultant powders were investigated. Compositional, microstructural, physical, thermal and optical properties of the powders obtained throughout the different process steps were characterized by using an X-ray diffractometry (XRD), particle size analysis (PSA), stereomicroscopy (SM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), gas pycnometry, differential scanning calorimetry (DSC), heating stage microscopy (HSM), atomic absorption spectrometry (AAS), Fourier transform infrared (FTIR) spectrometry and ultraviolet-visible spectrophotometry (UV-vis) techniques. Fine-grained and pure SmBO3 powders were successfully synthesized via a simple, feasible and scalable route, yielding both triclinic and hexagonal crystal structures. Triclinic SmBO3 powders were synthesized after mechanical activation for 1 h and annealing at 700 degrees C for 2 h. The polymorphic transformation temperature of SmBO3 powders from triclinic to hexagonal is about 1080 degrees C. Due to the effect of mechanical activation, the synthesis of triclinic SmBO3 phase and its transformation to hexagonal form were found to take place at similar to 50-100 degrees C lower temperatures than those reported in other methods. Mainly hexagonal SmBO3 powders were obtained after annealing at 1150 degrees C in the presence of a very small amount of triclinic SmBO3. The resultant powders showed intense UV absorptions in the range between 1025 and 1150 nm with minimum reflectivity of 0.57% (triclinic SmBO3 phase) and 0.68% (hexagonal SmBO3 phase) depending on their crystal structures. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
