Browsing by Publisher "Korean Institute of Metals and Materials"

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    Effect of Alternative Boronizing Mixtures on Boride Layer and Tribological Behaviour of Boronized SAE 1020 Steel
    (Korean Institute of Metals and Materials, 2022) Türkmen İ.; Yalamaç E.
    Abstract: In this study, SAE 1020 steel samples were boronized at 850 °C for 4 h with different boronizing mixtures by powder-pack boronizing method. H3BO3 or Na2B8O13 was used as the boron source, KBF4 or NaBF4 was used as the activator and SiC was used as the diluent. Thus, 4 different boronizing mixtures (M1-M4) were prepared. Thickness, morphology and phase structure of the formed boride layers were studied by X-ray diffraction and microstructural analyzes. The single phase (Fe2B) boride layer with saw-tooth morphology was formed on surface of the samples. The thickest boride layers were obtained by using M1 and M2 boronizing mixtures. Microhardness measurements were performed to determine hardness of the 3 zones (core, transition zone and boride layer). The means of boride layer hardness of the samples were compared according to 95% Confidence Intervals analysis. It was determined that the average hardness value of the boride layers was about 1475 HV. Wear tests were fulfilled by ball on disc type wear test method under dry sliding condition and at 25 °C. According to the friction coefficient and specific wear rate values of boronized samples, it was identified that the sample SM4 boronized with M4 boronizing mixture has the lowest wear rate (1.64 mm3/N.m) and friction coefficient value (0.63). Graphic Abstract: [Figure not available: see fulltext.] © 2021, The Korean Institute of Metals and Materials.
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    Characterization and Tribological Properties of Novel AlCu4.5SiMg Alloy–(B4C/TiO2/nGr) Quaternary Hybrid Composites Sintered via Microwave
    (Korean Institute of Metals and Materials, 2022) Ayvaz M.
    Abstract: In the future, hybrid aluminum matrix composites, which are the second generation composites, will be replaced by solid reinforced third-generation quaternary hybrid composites in which nano- and micro-scale reinforcement particles are used together. In this study, microwave sinterability of B4C, TiO2 (nm + µm), and nGr reinforced quaternary hybrid composites that had AlCu4.5SiMg alloyed Matrix, and their microstructural and tribological properties after sintering were examined. The proportion of nGr in the composite sample was taken as 0.5 wt%, while B4C and TiO2 were used in three different proportions (3, 9, 12 wt%). After being compressed under 600 MPa pressure, the composite samples were sintered for 60 min at 550 °C by a microwave oven with a power of 2.9 kW and a frequency of 2.45 GHz. It was determined that due to its high microwave absorbency, B4C reinforcement improved the microwave sinterability more compared to TiO2. In XRD analyses, whereas Al4C3 and Al3BC reaction products were not seen as harmful, the intermetallic phase of Al2Cu was detected. It was determined that both friction coefficient and wear resistance increased as the proportion of B4C increased in composite samples. In AlCu4.5SiMg–(12 wt% B4C/3 wt% TiO2/0.5 wt% nGr) quaternary hybrid composites with the highest hardness (97.6 HV), the lowest specific wear rate (0.118 mm3 Nm × 10−3) was detected. Graphic Abstract: [Figure not available: see fulltext.]. © 2020, The Korean Institute of Metals and Materials.
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    Properties of Aluminum Nano Composites Bearing Alumina Particles and Multiwall Carbon Nanotubes Manufactured by Mechanical Alloying and Microwave Sintering
    (Korean Institute of Metals and Materials, 2023) Özer E.; Ayvaz M.; Übeyli M.; Sarpkaya İ.
    Abstract: In this research, the effects of heat treatment and hybrid reinforcement ratio on the microstructural and mechanical properties of Al–4Cu nanocomposites containing MWCNT and nano Al2O3p were investigated. First of all, the hybrid reinforced Al–4Cu nanocomposites were manufactured with the aid of mechanical alloying and microwave sintering. And then, they were subjected to various heat treatments; annealing and artificial aging at 170, 180 and 200 °C individually. After that, the microstructural observations were made using X-ray diffraction, optical microscope and scanning electron microscopes (SEMs). The secondary electrons (SE), back scattered electrons (BSE), energy dispersive X-ray (EDX) and elemental mapping analyses of the specimens were carried out with the aid of SEMs. In addition, the nanoindentation tests were done to get the nanohardness and elastic modulus of composites. Finally, the composites were subjected to the compression test to clarify their compressive properties. The Al2Cu and Al4C3 precipitates were detected in the composite samples either annealed or peak-aged at 200 °C, while the intermetallic compound, Al7Cu2Fe, precipitated only in the aged samples. A significant increment in the nanohardness of composites was obtained with increasing reinforcement content. Moreover, the elastic modulus of annealed and peak-aged composites, reinforced with 15% hybrid reinforcement in volume, increased by 59% and 57%, respectively compared to the unreinforced alloy. Furthermore, the use of hybrid reinforcement in the alloy matrix allowed an improvement of compressive yield strength at the expense of compressive strain. Graphical Abstract: [Figure not available: see fulltext.]. © 2022, The Author(s) under exclusive licence to The Korean Institute of Metals and Materials.