The Experts below are selected from a list of 1677 Experts worldwide ranked by ideXlab platform
Helmut Clemens - One of the best experts on this subject based on the ideXlab platform.
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Study of nanometer-scaled lamellar microstructure in a Ti–45Al–7.5Nb alloy – Experiments and modeling
Intermetallics, 2010Co-Authors: Franz Dieter Fischer, Thomas Waitz, C.-h. Scheu, Limei Cha, Gerhard Dehm, Thomas Antretter, Helmut ClemensAbstract:Abstract Quenching of Ti–45 at%Al–7.5 at%Nb from the single α-phase region to room Temperature followed by aging below the Eutectoid Temperature leads to the precipitation of ultra-fine γ-TiAl lamellae. In addition to an extensive experimental program, reported by Cha et al. in Intermetallics 16 (2008) 868–875, in this work a micromechanical and thermodynamical model is presented for the formation of γ-TiAl lamellae within the α 2 -Ti 3 Al parent phase. A global transformation condition allows to predict a thickness to length ratio in accordance with experimental observations. Furthermore, a local transformation condition offers the basis for a kinetic law. The modeling concept can be applied to similar problems of combined diffusive and displacive phase transformations.
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In situ high-energy X-ray diffraction study and quantitative phase analysis in the α + γ phase field of titanium aluminides
Scripta Materialia, 2007Co-Authors: Lareine A. Yeoh, Klaus-dieter Liss, Arno Bartels, Harald F. Chladil, Maxim Avdeev, Helmut Clemens, Rainer Gerling, Thomas BuslapsAbstract:Quantitative atomic structure and phase analysis in the titanium aluminide intermetallic system of composition Ti–45Al–7.5Nb–0.5C (at.%) was conducted in situ by use of high-energy X-ray diffraction from a synchrotron and evaluated using the Rietveld method, implementing a model for atomic order in the α-phase which describes the order to disorder transition α 2 → α at the Eutectoid Temperature. The order parameter exhibits unexpected behavior and is entangled with the competition of different kinetic processes.
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Phase transformations in high niobium and carbon containing γ-TiAl based alloys
Intermetallics, 2006Co-Authors: Harald F. Chladil, Arno Bartels, Helmut Clemens, Rainer Gerling, Harald Leitner, F.-p. Schimansky, Sascha KremmerAbstract:Abstract Phase transformations and phase transition Temperatures in Ti–45 at.%Al alloyed with different amounts of niobium and carbon were investigated. Scanning electron microscopy, electron back-scattered diffraction and differential scanning calorimetry were applied for the characterisation of the prevailing phases and phase transformations. Both, niobium and carbon display a tendency to increase the Eutectoid Temperature, with carbon showing the stronger effect. In contrast, the influence of niobium and carbon on the α-transus Temperature is rather small. Thermodynamic equilibrium calculations were performed with the aid of the software ThermoCalc and MatCalc on the basis of a commercially available TiAl database. Partly, the calculated data show significant differences when compared to experimental results.
H.j. Rack - One of the best experts on this subject based on the ideXlab platform.
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Effect of vanadium on elevated Temperature phase relations in titanium aluminides containing 44 at.% Al
Materials Science and Engineering: A, 1992Co-Authors: Prabir K Chaudhury, Marc Long, H.j. RackAbstract:Abstract Differential scanning calorimetry, complemented by in situ high Temperature X-ray diffraction, has been utilized to examine phase stability in vanadium-containing TiAl(L1 0 ) alloys over the Temperature range 298–1773 K. Observations from alloys containing 4, 7 and 15at.%V-44at.%Al-bal. Ti have shown that increasing vanadium content results in the stabilization of the b.c.c., β, phase throughout the investigated Temperature range. These additions of vanadium do not, however, influence either the α → α 2 + γ Eutectoid Temperature or the stability of α 2 within the α + α 2 + β phase region.
Harald F. Chladil - One of the best experts on this subject based on the ideXlab platform.
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In situ high-energy X-ray diffraction study and quantitative phase analysis in the α + γ phase field of titanium aluminides
Scripta Materialia, 2007Co-Authors: Lareine A. Yeoh, Klaus-dieter Liss, Arno Bartels, Harald F. Chladil, Maxim Avdeev, Helmut Clemens, Rainer Gerling, Thomas BuslapsAbstract:Quantitative atomic structure and phase analysis in the titanium aluminide intermetallic system of composition Ti–45Al–7.5Nb–0.5C (at.%) was conducted in situ by use of high-energy X-ray diffraction from a synchrotron and evaluated using the Rietveld method, implementing a model for atomic order in the α-phase which describes the order to disorder transition α 2 → α at the Eutectoid Temperature. The order parameter exhibits unexpected behavior and is entangled with the competition of different kinetic processes.
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Phase transformations in high niobium and carbon containing γ-TiAl based alloys
Intermetallics, 2006Co-Authors: Harald F. Chladil, Arno Bartels, Helmut Clemens, Rainer Gerling, Harald Leitner, F.-p. Schimansky, Sascha KremmerAbstract:Abstract Phase transformations and phase transition Temperatures in Ti–45 at.%Al alloyed with different amounts of niobium and carbon were investigated. Scanning electron microscopy, electron back-scattered diffraction and differential scanning calorimetry were applied for the characterisation of the prevailing phases and phase transformations. Both, niobium and carbon display a tendency to increase the Eutectoid Temperature, with carbon showing the stronger effect. In contrast, the influence of niobium and carbon on the α-transus Temperature is rather small. Thermodynamic equilibrium calculations were performed with the aid of the software ThermoCalc and MatCalc on the basis of a commercially available TiAl database. Partly, the calculated data show significant differences when compared to experimental results.
Arno Bartels - One of the best experts on this subject based on the ideXlab platform.
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In situ high-energy X-ray diffraction study and quantitative phase analysis in the α + γ phase field of titanium aluminides
Scripta Materialia, 2007Co-Authors: Lareine A. Yeoh, Klaus-dieter Liss, Arno Bartels, Harald F. Chladil, Maxim Avdeev, Helmut Clemens, Rainer Gerling, Thomas BuslapsAbstract:Quantitative atomic structure and phase analysis in the titanium aluminide intermetallic system of composition Ti–45Al–7.5Nb–0.5C (at.%) was conducted in situ by use of high-energy X-ray diffraction from a synchrotron and evaluated using the Rietveld method, implementing a model for atomic order in the α-phase which describes the order to disorder transition α 2 → α at the Eutectoid Temperature. The order parameter exhibits unexpected behavior and is entangled with the competition of different kinetic processes.
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Phase transformations in high niobium and carbon containing γ-TiAl based alloys
Intermetallics, 2006Co-Authors: Harald F. Chladil, Arno Bartels, Helmut Clemens, Rainer Gerling, Harald Leitner, F.-p. Schimansky, Sascha KremmerAbstract:Abstract Phase transformations and phase transition Temperatures in Ti–45 at.%Al alloyed with different amounts of niobium and carbon were investigated. Scanning electron microscopy, electron back-scattered diffraction and differential scanning calorimetry were applied for the characterisation of the prevailing phases and phase transformations. Both, niobium and carbon display a tendency to increase the Eutectoid Temperature, with carbon showing the stronger effect. In contrast, the influence of niobium and carbon on the α-transus Temperature is rather small. Thermodynamic equilibrium calculations were performed with the aid of the software ThermoCalc and MatCalc on the basis of a commercially available TiAl database. Partly, the calculated data show significant differences when compared to experimental results.
Rainer Gerling - One of the best experts on this subject based on the ideXlab platform.
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In situ high-energy X-ray diffraction study and quantitative phase analysis in the α + γ phase field of titanium aluminides
Scripta Materialia, 2007Co-Authors: Lareine A. Yeoh, Klaus-dieter Liss, Arno Bartels, Harald F. Chladil, Maxim Avdeev, Helmut Clemens, Rainer Gerling, Thomas BuslapsAbstract:Quantitative atomic structure and phase analysis in the titanium aluminide intermetallic system of composition Ti–45Al–7.5Nb–0.5C (at.%) was conducted in situ by use of high-energy X-ray diffraction from a synchrotron and evaluated using the Rietveld method, implementing a model for atomic order in the α-phase which describes the order to disorder transition α 2 → α at the Eutectoid Temperature. The order parameter exhibits unexpected behavior and is entangled with the competition of different kinetic processes.
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Phase transformations in high niobium and carbon containing γ-TiAl based alloys
Intermetallics, 2006Co-Authors: Harald F. Chladil, Arno Bartels, Helmut Clemens, Rainer Gerling, Harald Leitner, F.-p. Schimansky, Sascha KremmerAbstract:Abstract Phase transformations and phase transition Temperatures in Ti–45 at.%Al alloyed with different amounts of niobium and carbon were investigated. Scanning electron microscopy, electron back-scattered diffraction and differential scanning calorimetry were applied for the characterisation of the prevailing phases and phase transformations. Both, niobium and carbon display a tendency to increase the Eutectoid Temperature, with carbon showing the stronger effect. In contrast, the influence of niobium and carbon on the α-transus Temperature is rather small. Thermodynamic equilibrium calculations were performed with the aid of the software ThermoCalc and MatCalc on the basis of a commercially available TiAl database. Partly, the calculated data show significant differences when compared to experimental results.
