The Experts below are selected from a list of 4356 Experts worldwide ranked by ideXlab platform
A K Mukherjee - One of the best experts on this subject based on the ideXlab platform.
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spark plasma sintering of an infrared transparent y2o3 mgo nanocomposite
Journal of the American Ceramic Society, 2010Co-Authors: Dongtao Jiang, A K MukherjeeAbstract:A novel optically transparent ceramic nanocomposite Y2O3–MgO was produced using spark plasma sintering technique. Sintering parameters was optimized to obtain Fully Dense Material while maintaining nanoscale grain size. The sintered nanocomposite has an excellent infrared transmission as a result of small grain size and homogeneous microstructure. Postsinter annealing can significantly improve the transmission. Overly larger grain size severely degrades the transmittance.
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Spark Plasma Sintering of an Infrared‐Transparent Y2O3–MgO Nanocomposite
Journal of the American Ceramic Society, 2010Co-Authors: Dongtao Jiang, A K MukherjeeAbstract:A novel optically transparent ceramic nanocomposite Y2O3–MgO was produced using spark plasma sintering technique. Sintering parameters was optimized to obtain Fully Dense Material while maintaining nanoscale grain size. The sintered nanocomposite has an excellent infrared transmission as a result of small grain size and homogeneous microstructure. Postsinter annealing can significantly improve the transmission. Overly larger grain size severely degrades the transmittance.
Dongtao Jiang - One of the best experts on this subject based on the ideXlab platform.
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spark plasma sintering of an infrared transparent y2o3 mgo nanocomposite
Journal of the American Ceramic Society, 2010Co-Authors: Dongtao Jiang, A K MukherjeeAbstract:A novel optically transparent ceramic nanocomposite Y2O3–MgO was produced using spark plasma sintering technique. Sintering parameters was optimized to obtain Fully Dense Material while maintaining nanoscale grain size. The sintered nanocomposite has an excellent infrared transmission as a result of small grain size and homogeneous microstructure. Postsinter annealing can significantly improve the transmission. Overly larger grain size severely degrades the transmittance.
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Spark Plasma Sintering of an Infrared‐Transparent Y2O3–MgO Nanocomposite
Journal of the American Ceramic Society, 2010Co-Authors: Dongtao Jiang, A K MukherjeeAbstract:A novel optically transparent ceramic nanocomposite Y2O3–MgO was produced using spark plasma sintering technique. Sintering parameters was optimized to obtain Fully Dense Material while maintaining nanoscale grain size. The sintered nanocomposite has an excellent infrared transmission as a result of small grain size and homogeneous microstructure. Postsinter annealing can significantly improve the transmission. Overly larger grain size severely degrades the transmittance.
I. Iturriza - One of the best experts on this subject based on the ideXlab platform.
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Self-passivating W-Cr-Y alloys: Characterization and testing
Fusion Engineering and Design, 2017Co-Authors: A. Calvo, I. Iturriza, Carmen García-rosales, N. Ordás, Karsten Schlueter, Freimut Koch, Gerald Pintsuk, E. Tejado, Jose Ygnacio PastorAbstract:Abstract The use of self-passivating tungsten alloys for the first wall armor of future fusion reactors is advantageous concerning safety issues in comparison with pure tungsten. Bulk W-10Cr-0.5Y alloy manufactured by mechanical alloying followed by HIP resulted in a Fully Dense Material with grain size around 100 nm and a dispersion of Y-rich oxide nanoparticles located at the grain boundaries. An improvement in flexural strength and fracture toughness was observed with respect to previous works. Oxidation tests under isothermal and accident-like conditions revealed a very promising oxidation behavior for the W-10Cr-0.5Y alloy. Thermo-shock tests at JUDITH-1 to simulate ELM-like loads resulted in a crack network at the surface with roughness values lower than those of a pure W reference Material. An additional thermal treatment at 1550 °C improves slightly the oxidation and significantly thermo-shock resistance of the alloy.
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Development of powder metallurgy T42 high speed steel for structural applications
Journal of Materials Processing Technology, 2008Co-Authors: V. Trabadelo, S. Giménez, I. IturrizaAbstract:Abstract Water atomized T42 high speed steel powders have been processed by a powder metallurgy (PM) route in order to obtain a Fully Dense Material suitable for valve seat inserts (VSI) in diesel engines. Two different heat treatments (isothermal annealing and multitempering) were designed leading to the targeted hardness value (50 HRC). Microstructural characterisation of the heat-treated Material was carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fracture strength and fracture toughness have also been investigated. The wear behaviour was evaluated through pin-on-disc tests at service temperature (360 °C). The obtained results demonstrated the excellent wear resistance of the VSI Material without severe wear of the counterMaterial (valve).
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Microstructural characterisation of powder metallurgy M35MHV HSS as a function of the processing route
Journal of Materials Processing Technology, 2003Co-Authors: S. Giménez, I. IturrizaAbstract:Abstract The microstructure of powder metallurgy M35MHV (1.8C; 4.2V) HSS has been analysed as a function of the processing route. Four different sintering methods have been applied to obtain Fully Dense Materials (density>99% TD) from water atomised powders. Variables such as previous austenite grain size, type and amount of carbides and the phases present in the as-sinter condition have been analysed. Hot isostatic pressing (HIP) is giving a Fully Dense Material at 1100 °C, 150 MPa and 15 min holding time with a very fine microstructure (mean grain size smaller than 3 μm) as a result of a solid state densification process. As a supersolidus liquid phase sintering (SLPS) process, vacuum sintering needs 1220 °C to obtain full densification with a mean grain size of 16.9 μm. Improving the sinterability by means of the use of nitrogen, atmosphere sintering is carried out at 1140 °C under industrial atmosphere ( 90% N 2 +9% H 2 +1% CH 4 ) giving a mean grain size of 10.0 μm. Finally sinter-HIP under 4 bar of nitrogen is responsible for an optimum sintering temperature (OST) as low as 1100 °C. In specimens sintered under this last condition, the microstructure is rough with a total amount of carbides of 28 vol.%. ThermoCalc calculations have helped for understanding both sintering behaviour and microstructure.
Allison M Beese - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the strength of support structures used in powder bed fusion additive manufacturing of Ti-6Al-4V
Additive Manufacturing, 2017Co-Authors: Lourdes D. Bobbio, Shipin Qin, Alexander Dunbar, Panagiotis Michaleris, Allison M BeeseAbstract:Support structures are required in powder bed fusion (PBF) additive manufacturing of metallic components with overhanging structures in order to reinforce and anchor the part, preventing warping during fabrication. In this study, we tested the tensile structural strength of support structures with four different 2-dimensional lattice geometries by fabricating samples composed of solid Material on the bottom, followed by support Material in the middle, followed by solid Material on the top. The support structure regions were fabricated with a lower linear heat input than the solid Material, providing deliberate geometrical stress concentrations to enable the removal of support Material after processing. These samples were subjected to tension in the vertical direction to measure the strengths of the support structure-solid Material interfaces. Two strengths were computed: an effective structural strength defined as the total force that the structure withstood normalized by the full cross-sectional area, and a ligament structural strength, defined as the effective structural strength normalized by the density of the solid Material, thereby ignoring the volume of the surrounding powder and voids that do not contribute to the strength of the lattice. The effective structural strength was 14–32% of the strength of Fully Dense Ti-6Al-4V made by PBF and the ligament structural strength was 34–49% of the strength of Fully Dense Material. These interface strengths are lower than that of Fully-Dense Material due to the stress concentrations at the support structure-solid Material interfaces, not any intrinsic difference in the intrinsic strength of support structure versus solid Material. These results can be used to tailor the support structure geometry to balance sufficient anchoring strength during fabrication and ease of part removal and subsequent machining during post-processing.
Vladimir Brailovski - One of the best experts on this subject based on the ideXlab platform.
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Density Dependence of the Macroscale Superelastic Behavior of Porous Shape Memory Alloys: A Two-Dimensional Approach
Smart Materials Research, 2013Co-Authors: Guillaume Maîtrejean, Patrick Terriault, Vladimir BrailovskiAbstract:Porous Shape Memory Alloys (SMAs) are of particular interest for many industrial applications, as they combine intrinsic SMA (shape memory effect and superelasticity) and foam characteristics. The computational cost of direct porous Material modeling is however extremely high, and so designing porous SMA structure poses a considerable challenge. In this study, an attempt is made to simulate the superelastic behavior of porous Materials via the modeling of Fully Dense structures with Material properties modified using a porous/bulk density ratio scaling relation. Using this approach, direct modeling of the porous microstructure is avoided, and only the macroscale response of the model is considered which contributes to a drastic reduction of the computational cost. Foam structures with a gradient of porosity are also studied, and the prediction made using the Fully Dense Material model is shown to be in agreement with the mesoscale porous Material model.
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Density dependence of the superelastic behavior of porous shape memory alloys: Representative Volume Element and scaling relation approaches
Computational Materials Science, 2013Co-Authors: Guillaume Maîtrejean, Patrick Terriault, Vladimir BrailovskiAbstract:Abstract As the use of Shape Memory Alloys (SMAs) grows increasingly common in many industrial applications, the porous form of SMA is of particular interest as it associates both the shape memory effect and superelasticity with the characteristics of foam. However, numerical prediction of the mechanical response of SMA foam is very challenging due to the micro–macro nature exhibited by the Material, as the porous microstructure is several orders of magnitude smaller than the overall dimensions of the macroscopic porous sample. To circumvent, or at least alleviate this computational weight, an attempt is made to describe the superelastic behavior of SMA foams using two approaches: Representative Volume Element (RVE) and scaling relation; the latter is based on modeling the Fully-Dense Material with mechanical properties equivalent to those of its porous counterpart. This approach avoids direct modeling of the porous microstructure and thus contributes to a drastic reduction of the computational cost. A validation is made by comparing the numerical results obtained in this study with experimental results taken from the literature.
