The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
Graeme Ackland - One of the best experts on this subject based on the ideXlab platform.
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high temperature oxidation resistance in titanium Niobium Alloys
Journal of Alloys and Compounds, 2015Co-Authors: Bengt E Tegner, Linggang Zhu, Carsten Siemers, Karel Saksl, Graeme AcklandAbstract:Abstract Titanium Alloys are ideally suited for use as lightweight structural materials, but their use at high temperature is severely restricted by oxidation. Niobium is known to confer oxidation-resistance, and here we disprove the normal explanation, that Nb5+ ions trap oxygen vacancies. Using density functional theory calculation, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) we show that Nb is insoluble in TiO2. In fact, the Ti–Nb surface has three-layer structure: the oxide itself, an additional Nb-depleted zone below the oxide and a deeper sublayer of enhanced Nb. Microfocussed X-ray diffraction also demonstrates recrystallization in the Nb-depleted zone. We interpret this using a dynamical model: slow Nb-diffusion leads to the build up of a Nb-rich sublayer, which in turn blocks oxygen diffusion. Nb effects contrast with vanadium, where faster diffusion prevents the build up of equivalent structures.
L C Brinson - One of the best experts on this subject based on the ideXlab platform.
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Model for high-strain-rate deformation of uranium–Niobium Alloys
Journal of Applied Physics, 2003Co-Authors: Francis L Addessio, Q H Zuo, T A Mason, L C BrinsonAbstract:A thermodynamic approach is used to develop a framework for modeling uranium–Niobium Alloys under the conditions of high-strain rate. Using this framework, a three-dimensional phenomenological model, which includes nonlinear elasticity (equation of state), phase transformation, crystal reorientation, rate-dependent plasticity, and porosity growth, is presented. An implicit numerical technique is used to solve the evolution equations for the material state. Comparisons are made between the model and data for low-strain rate loading and unloading as well as heating and cooling experiments. Comparisons of the model and data also are made for low- and high-strain-rate uniaxial stress and uniaxial strain experiments. A uranium–6 wt % Niobium alloy is used in comparisons of the model and experiment.
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model for high strain rate deformation of uranium Niobium Alloys
Journal of Applied Physics, 2003Co-Authors: Francis L Addessio, Q H Zuo, T A Mason, L C BrinsonAbstract:A thermodynamic approach is used to develop a framework for modeling uranium–Niobium Alloys under the conditions of high-strain rate. Using this framework, a three-dimensional phenomenological model, which includes nonlinear elasticity (equation of state), phase transformation, crystal reorientation, rate-dependent plasticity, and porosity growth, is presented. An implicit numerical technique is used to solve the evolution equations for the material state. Comparisons are made between the model and data for low-strain rate loading and unloading as well as heating and cooling experiments. Comparisons of the model and data also are made for low- and high-strain-rate uniaxial stress and uniaxial strain experiments. A uranium–6 wt % Niobium alloy is used in comparisons of the model and experiment.
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A Model for High-Strain-Rate Deformation of Uranium-Niobium Alloys
2003Co-Authors: Francis L Addessio, Q H Zuo, T A Mason, L C BrinsonAbstract:A thermodynamic approach is used to develop a framework for modeling uranium-Niobium Alloys under the conditions of high strain rate. Using this framework, a three-dimensional phenomenological model, which includes nonlinear elasticity (equation of state), phase transformation, crystal reorientation, rate-dependent plasticity, and porosity growth is presented. An implicit numerical technique is used to solve the evolution equations for the material state. Comparisons are made between the model and data for low-strain-rate loading and unloading as well as for heating and cooling experiments. Comparisons of the model and data also are made for low- and high-strain-rate uniaxial stress and uniaxial strain experiments. A uranium-6 weight percent Niobium alloy is used in the comparisons of model and experiment.
Francesca Moret - One of the best experts on this subject based on the ideXlab platform.
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Experimental study of phase equilibria in the Nb-Ti-Al system
Scripta Materialia, 1999Co-Authors: V. Chaumat, Emilie Ressouche, P. Desre, Bachir Ouladdiaf, Francesca MoretAbstract:To improve the performance of aircraft engines and of some nuclear devices, it is necessary to increase service temperature of hot components working in high temperature environments, from 1,100 to 1,900 K. In this context, Niobium Alloys of the Nb-Ti-Al system are studied. The existence of an ordered cubic centered B2 phase (designed L2{sub 0} in ternary Alloys) around the composition Ti50-Nb25-Al25 (at.%) has been reported in the literature. In order to discuss the theoretical results, an experimental study by neutron diffraction has been undertaken.
T R G Kutty - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic investigations of uranium rich binary and ternary Alloys
Journal of Thermal Analysis and Calorimetry, 2013Co-Authors: Smruti Dash, Kaushik Ghoshal, T R G KuttyAbstract:Uranium–zirconium, uranium Niobium, and uranium–zirconium–Niobium Alloys were synthesized by the arc melting technique and their phase transition temperatures were determined using a high temperature calorimeter. Heat capacities of U–7 wt%Zr, U–7 wt%Nb, U–5 wt%Zr–2 wt%Nb, U–3.5 wt%Nb–3.5 wt%Zr, and U–2 wt%Zr–5 wt%Nb were measured using a differential scanning calorimeter in the temperature range 303–921 K. A set of self-consistent thermodynamic functions such as entropy, enthalpy, and Gibbs energy function data for these binary and ternary Alloys were reported for the first time using heat capacity data obtained in this study and required literature data.
Timothy W Ellis - One of the best experts on this subject based on the ideXlab platform.
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Metal matrix composites produced from yttrium based or high yttrium content Alloys
Journal of Alloys and Compounds, 1994Co-Authors: Timothy W EllisAbstract:Abstract This paper surveys the author's production of metal matrix composite from yttrium or high yttrium content Alloys. Composite materials have been produced by directional solidification and/or cooling in the yttrium—oxygen system. Additionally, metal—metal matrix composites were produced by deformation processing. These materials have been produced in the yttrium—titanium system and in the yttrium—Niobium system are analogous to those formed in copper—Niobium Alloys. Here a precursor alloy is cold worked such that both phases co-deform. This produces a fine filamentary reinforcing phase within a continuous matrix phase. Both methods produce materials with interesting microstructures and possible new methods for the production of structural materials from yttrium, scandium or the other rare earth metals.
