Metal, Ceramic and Composite Materials

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Authors: In Won Kim, Sun Ig Hong
Abstract: Creep properties of one-step and two-step annealed Zr-1Nb-0.12O cladding tubes were studied. Creep tests were carried out at 450~500 °C with the applied stress between 80MPa and 120MPa The creep rates of the two-step annealed Zr-1Nb-0.12O alloy were found to be slower than those of the one-step annealed Zr-1Nb-0.12O alloy. The creep rate decreased with increase of grain size with annealing for Zr-1Nb-0.12O at intermediate temperatures, suggesting the creep resistance can be enhanced by the grain size control. The creep life of two-step annealed Zr-1Nb-0.12O increased over the one-step annealed Zr-1Nb-0.12O by the factor of 18~20 despite the greater initial instantaneous strain.
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Authors: Won Nyeon Kim, In Kyu Kim, Sun Ig Hong
Abstract: The tensile mechanical performance and ductility of Cu/Al/Cu clad composite were studied. Brittle interfacial reaction compounds were observed at Cu/Al interfaces after annealing at 500°C. The ultimate tensile strength of the tri-layered Cu/Al/Cu clad plates is in close agreement with those calculated from the UTS data of separated Cu and Al layers using the rule of mixture. The loss of ductility in Cu/Al/Cu and separate Cu upon annealing at 500°C is associated with the brittle intermetallic layer. The greater ductility of as-roll-bonded Cu/Al/Cu than those of both Cu and Al is linked to the excellent interface bonding after roll-bonding. Excellent bonding at Cu/Al interface is prerequisites for improvement ductility of clad composite.
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Authors: Hua Hu, Jun Lin Xie, De Fang, Feng He
Abstract: The Co-Mn/TiO2 catalysts with different contents of Co were prepared by the impregnation method. Catalytic activity tests showed that the addition of Co could obviously enhance the SCR performance of Mn/TiO2 catalyst, and the NO conversion of 0.05Co-Mn/TiO2 samples could reach 94.03% at 180 °C. At the same time, with the help of XRD, BET, H2-TPR and NH3-TPD, the various physical and chemical characteristics as well as phase structures of catalysts were characterized systematically. According to the results, the formations of crystalline CoMn2O4, Mn3O4 and amorphous Mn2O3 were detected. Furthermore, Co doping could reduce the reduction temperatures of catalysts and enhance the adsorption capacities of NH3, resulting in the excellent SCR performance at low temperature.
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Authors: Ho Kyun Oh, Sang Min Park, Sun Ig Hong
Abstract: Hot compressive deformation and cracking behaviors of cast 21-4N steel were investigated over a temperature range between 900°C~1250°C. The strength of the specimen at the outer surface of ingot is greater than that in the inner part because of the initial rapid solidification and corresponding fine structure at the outer surface. The initial flow stress hump in the stress-strain curves can be attributed to the dynamic recrystallization, which requires the initial strain energy build-up before the activation of grain nucleation process. With increase of temperature the critical stain for dynamic recrystallization decreases and at high enough temperatures, no critical strain for the build-up of strain energy is needed. At temperatures between 1000°C and 1200°C, homogeneous deformation occurred and no cracks were observed even after 50% strain. The cracks observed below 1000°C could be associated with the more difficult plastic flow in the presence of carbides and nitrides. The presence of fatal crack at 1250°C and the loss of hot ductility can be attributed to the partial melting in austenite grain boundaries at high temperatures.
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Authors: Feng Lin Xu, Bo Li, Hong Bo Wang, Jin Jin Wu, Dong Feng Li, Cheng Hou Zhou, Xiao Min Wang
Abstract: In this study, we designed four components of 6N01 aluminum alloy by orthogonal design, and analyzed the effect of the different elements for the mechanical properties and microstructure of the designed material after casting, homogenization annealing, extrusion treatment and natural aging. Considering the above series of tests of the data indicators, and thus orthogonal filter out two materials that all aspects of performance are more excellent.Keywords: orthogonal design; 6N01 aluminum alloy; mechanical properties; microstructure
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Authors: Yu Yen Cheng, Mei Fang Lu, Jim Jui Min Lin
Abstract: While conducting research for dioxin emission factor for stationary source emission, it is found that some factors come from overestimation. The cause of discrepancy for estimating process comes often from lacking understanding of the process. The result of this study for secondary aluminum refining emission factors indicates that if raw materials are scraps, the factors averaged at 541 ng I-TEQ/Ton-raw materials. If waste aluminum is used as the raw material, factors averaged at 1338 ng I-TEQ/Ton-raw material. The factors based on site sampling for coal-fired power generation process is 24.84-549.62 ng I-TEQ/Ton-fuel. It varies according to coal sources. Emission factor for cement producing process is 95.4-102.66 ng I-TEQ/Ton-raw material. Due to fewer differences in operating traits, raw materials and fuel application for cement producing process, emission factors have smaller differences. The reliability for emission variables is relatively higher.
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Authors: Junji Sakamoto, Yong Sung Lee, Seong Kyun Cheong
Abstract: The relations between shot peening coverage and fatigue strength in the quenched-tempered and annealed medium-carbon steels and aluminum alloy A7075-T6 were experimentally studied using a rotating bending fatigue testing machine. It was found that the fatigue strengths of the annealed steel and aluminum alloy were increased by shot peening. On the other hand, the fatigue strength of the quenched-tempered steel were not increased by shot peening. Same shot peening condition causes the positive effect and the negative effect depending on the type of material. Moreover, the valuable coverage might depend on the type of material. More detailed work is necessary to resolve the issue.
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Authors: Ding Zhang, Wen Yong Ding, Feng Su, Shi Jiao Jin
Abstract: Composite patch adhesively bonded repair is an advanced repairing method for damaged metallic structure, and patch designing is important before repairing, which decides final repairing effect. Based on 3D FEM, the model of aluminum plate with a central through crack adhesively bonded repaired with composite patch was established, which can take into account residual thermal stress and bending deformation caused by differences of thermal expansion coefficient. SIF was calculated using virtual crack closure technology and compared to evaluate patch designing. The results show that for through centrally cracked aluminum plate, rectangle boron/epoxy patch is the best, and more plies whose fiber direction is parallel to loading direction are, better repairing can be got.
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Authors: Koshiro Mizobe, Katsuyuki Kida, Wakana Matsuda, Kazuaki Nakane
Abstract: Grain refinement has a strong influence on material strength. Therefore, the automatic evaluation method of the grain refinement level is useful. In order to develop a grain size analysis system, we applied the homology theory to prior austenite grain analysis. We prepared repeatedly quenched high-carbon high-chromium steel samples (JIS-SUJ2) and evaluated their microstructures in order to investigate the relation between the Betti numbers (b0 and b1) and prior austenite grains. We found that the Betti number (b1) is strongly correlated to the number of grains.
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