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G Eggeler - One of the best experts on this subject based on the ideXlab platform.
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the nucleation of mo rich Laves Phase particles adjacent to m23c6 micrograin boundary carbides in 12 cr tempered martensite ferritic steels
Acta Materialia, 2015Co-Authors: M I Isik, Aleksander Kostka, Victoria A Yardley, Konda Gokuldoss Pradeep, Maria Jazmin Duarte, Pyuckpa Choi, Dierk Raabe, G EggelerAbstract:Abstract We study the nucleation of Mo-rich Laves Phase particles during aging and creep of 12 wt.% Cr tempered martensite ferritic steels (TMFS). Recently, in Isik et al. (2014) we reported that Laves Phase particles tend to form at micrograin boundaries of TMFSs after Mo and Si had segregated from the ferritic matrix to these internal interfaces. In the present work, we employ transmission electron microscopy (TEM) and atom probe tomography (APT) to study the formation of Laves Phase particles. We investigate the preference of Laves Phase particles to nucleate next to M23C6 micrograin boundary carbides. Our results suggest that this joint precipitation effect is due to the combined segregation of Mo and Si from the matrix to the micrograin boundaries and Si and P enrichment around the growing carbides.
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on the nucleation of Laves Phase particles during high temperature exposure and creep of tempered martensite ferritic steels
Acta Materialia, 2014Co-Authors: M I Isik, Aleksander Kostka, G EggelerAbstract:Abstract This paper reports on the formation of an Mo-rich Laves Phase during high-temperature exposure and creep of a tempered martensite ferritic steel with 12 wt.% Cr and 1 wt.% Mo. The material was exposed to 550 °C for time intervals between 864 and 81,984 h. For comparison, a few creep tests were carried out at 550 °C and 120 MPa (duration between 864 and 12,456 h). All tests were interrupted after specific time periods and microstructures were investigated using transmission electron microscopy and atom probe tomography. Laves Phase formation occurs during both heat treatment and creep. Creep stress and strain have no significant effect on the early stages of Laves Phase formation. In the present work we show that prior to Laves Phase nucleation Si and Mo segregate to micrograin boundaries, where subsequently Laves Phase particles appear next to M 23 C 6 carbides.
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on the formation and growth of mo rich Laves Phase particles during long term creep of a 12 chromium tempered martensite ferritic steel
Scripta Materialia, 2009Co-Authors: A Aghajani, Frank Richter, Christoph Somsen, S G Fries, Ingo Steinbach, G EggelerAbstract:It was recently reported (Aghajani et al. [1] ) that Laves Phase particles do not reach thermodynamic equilibrium as they form and grow during long-term creep (120 MPa, 823 K, 139 971 h) of a 12% chromium tempered martensite ferritic steel. In the present work we show that this is due to the slow diffusion of silicon in the steel matrix.
Lixin Wang - One of the best experts on this subject based on the ideXlab platform.
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annealing effects on Laves Phase related body centered cubic solid solution metal hydride alloys
Journal of Alloys and Compounds, 2016Co-Authors: K Young, Taihei Ouchi, Jean Nei, Lixin WangAbstract:Abstract Effects of thermal annealing (between 800 and 1100 °C) on the structural, gaseous Phase and electrochemical hydrogen storage properties of a Laves Phase-related body-centered-cubic (BCC) alloy, Ti15.6Zr2.1V40.0Cr11.2Mn6.9Co1.4Ni22.5Al0.3, were studied. Only BCC, TiNi, and C14 Phases appeared in the as-cast sample. Annealing at 800 and 900 °C increased the main hydrogen storage BCC Phase abundance and reduced C14 and TiNi catalytic Phases. Annealing at 1000 °C promoted the formation of Ti2Ni Phase. A σ-VNi Phase appeared after annealing at 1100 °C. In addition, the annealed samples also contained Zr and TiO2 debris. Electrochemical results suggested optimized annealing conditions of 900 °C for 12-h to optimize the storage capacity, high-rate performance, and activation due to a favorable balance in abundance between storage Phase (BCC) and catalytic Phases (C14 and TiNi).
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structural hydrogen storage and electrochemical properties of Laves Phase related body centered cubic solid solution metal hydride alloys
International Journal of Hydrogen Energy, 2014Co-Authors: K Young, Jean Nei, Lixin Wang, D F WongAbstract:Abstract Structure, gaseous Phase hydrogen storage, and electrochemical properties of a series of Laves Phase-related BCC solid solution metal hydride alloys with BCC/C14 ratios ranging from 0.09 to 8.52 were studied. Some properties are correlated to the Phase abundance and V-content in the alloy with monotonic evolutions, for example, lattice constant, Phase abundance, and hydrogen storage pressure. Other properties such as gaseous Phase capacities, PCT hysteresis, high-rate dischargeability, and bulk hydrogen diffusion correlate better with the C14 Phase crystallite size, which are considered to be more related to the synergetic effect between main and secondary Phases. In contrast with conventional metal hydride alloys used in NiMH batteries, the electrochemical discharge capacities of these alloys are not between the maximum and the reversible hydrogen storage measured in the gaseous Phase. The current study's alloys have electrochemical capacities that are insensitive to composition but have much room for improvement, with high-rate dischargeabilities that are superior compared to other commercially available alloys. With further research, these alloys show potential for high-rate battery applications.
K Young - One of the best experts on this subject based on the ideXlab platform.
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annealing effects on Laves Phase related body centered cubic solid solution metal hydride alloys
Journal of Alloys and Compounds, 2016Co-Authors: K Young, Taihei Ouchi, Jean Nei, Lixin WangAbstract:Abstract Effects of thermal annealing (between 800 and 1100 °C) on the structural, gaseous Phase and electrochemical hydrogen storage properties of a Laves Phase-related body-centered-cubic (BCC) alloy, Ti15.6Zr2.1V40.0Cr11.2Mn6.9Co1.4Ni22.5Al0.3, were studied. Only BCC, TiNi, and C14 Phases appeared in the as-cast sample. Annealing at 800 and 900 °C increased the main hydrogen storage BCC Phase abundance and reduced C14 and TiNi catalytic Phases. Annealing at 1000 °C promoted the formation of Ti2Ni Phase. A σ-VNi Phase appeared after annealing at 1100 °C. In addition, the annealed samples also contained Zr and TiO2 debris. Electrochemical results suggested optimized annealing conditions of 900 °C for 12-h to optimize the storage capacity, high-rate performance, and activation due to a favorable balance in abundance between storage Phase (BCC) and catalytic Phases (C14 and TiNi).
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effects of cr zr v mn fe and co to the hydride properties of Laves Phase related body centered cubic solid solution alloys
Journal of Power Sources, 2015Co-Authors: K Young, Taihei Ouchi, Jean Nei, T MengAbstract:Abstract Chemical composition modifications of a Laves Phase-related BCC solid solution base alloy, Ti15.6Zr2.1V44Cr11.2Mn6.9Fe2.7Co1.4Ni15.7Al0.3, were investigated in order to study the function of each constituent element on the structural, gaseous Phase and electrochemical hydrogen storage properties of these alloys. In general, removal of Fe and decrease in V-content in exchange for higher Ni-content were found to improve both the electrochemical capacity and high-rate dischargeability, which are related to the decrease in C14-content and increase in TiNi-content. However, total elimination of the C14 Phase by removal of Zr resulted in a reduced discharge capacity, a prolonged activation period, and a less catalytic surface for electrochemical reaction. Besides the BCC and C14 Phases, the TiNi Phase was also found in every alloy in this study, contributing positively to the bulk diffusion of hydrogen while hindering the surface electrochemical reaction.
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structural hydrogen storage and electrochemical properties of Laves Phase related body centered cubic solid solution metal hydride alloys
International Journal of Hydrogen Energy, 2014Co-Authors: K Young, Jean Nei, Lixin Wang, D F WongAbstract:Abstract Structure, gaseous Phase hydrogen storage, and electrochemical properties of a series of Laves Phase-related BCC solid solution metal hydride alloys with BCC/C14 ratios ranging from 0.09 to 8.52 were studied. Some properties are correlated to the Phase abundance and V-content in the alloy with monotonic evolutions, for example, lattice constant, Phase abundance, and hydrogen storage pressure. Other properties such as gaseous Phase capacities, PCT hysteresis, high-rate dischargeability, and bulk hydrogen diffusion correlate better with the C14 Phase crystallite size, which are considered to be more related to the synergetic effect between main and secondary Phases. In contrast with conventional metal hydride alloys used in NiMH batteries, the electrochemical discharge capacities of these alloys are not between the maximum and the reversible hydrogen storage measured in the gaseous Phase. The current study's alloys have electrochemical capacities that are insensitive to composition but have much room for improvement, with high-rate dischargeabilities that are superior compared to other commercially available alloys. With further research, these alloys show potential for high-rate battery applications.
Gerhard Sauthoff - One of the best experts on this subject based on the ideXlab platform.
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the role of Laves Phase on microstructure evolution and creep strength of novel 9 cr heat resistant steels
Intermetallics, 2013Co-Authors: Gerhard Sauthoff, O Prat, Jose Garcia, D Rojas, Gerhard IndenAbstract:Abstract The influence of Laves Phase (type Fe2W) formation and growth kinetics on the creep strength at 650 °C of two different 9%Cr heat resistant steels of the authors' design was investigated. The microstructure evolution was characterized using transmission electron microscopy in the scanning mode (STEM). Kinetic modeling was carried out using the software DICTRA. STEM investigations revealed that the Laves Phase precipitates tend to form clusters, have an irregular shape and are often located close to M23C6 carbides, along martensite lath boundaries or sub-grain boundaries. DICTRA simulations showed that the growth kinetics of Laves Phase was high in the first thousand hours of creep, reaching its equilibrium volume fraction after 7000–10,000 h. Simultaneous competitive growth of M23C6 carbides and Laves Phase was simulated showing that Laves Phase grows very slowly to reach the final equilibrium Phase fraction only after almost 13,000 h, while M23C6 reached the equilibrium Phase fraction already during tempering. Best creep results were obtained for the 9%Cr alloy with low carbon content, reduced sub-grain growth, very slow coarsening of MX carbonitrides and slow growth of Laves Phase.
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Phase equilibria in the fe al mo system part i stability of the Laves Phase fe2mo and isothermal section at 800 c
Intermetallics, 2008Co-Authors: Markus Eumann, Gerhard Sauthoff, Martin PalmAbstract:Abstract Phase equilibria in the Fe–Al–Mo system were experimentally determined at 800 °C. From metallography, X-ray diffraction and electron probe microanalysis on equilibrated alloys and diffusion couples a complete isothermal section has been established. It is shown that the Laves Phase Fe2Mo is a stable Phase. The Phase Al4Mo, which only becomes stable above 942 °C in the binary system, is the only ternary compound found at 800 °C. For all binary Phases the solid solubility ranges for the third component have been established. The D03/B2 and B2/A2 transition temperatures have been determined for a selected alloy by differential thermal analysis and transmission electron microscopy. The results confirm that the D03/B2 transition temperature substantially increases by the addition of Mo, while the B2/A2 transition temperature is about that for a binary alloy with the same Al content.
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mechanical properties and oxidation behaviour of two Phase iron aluminium alloys with zr fe al 2 Laves Phase or zr fe al 12 τ1 Phase
Intermetallics, 2005Co-Authors: Frank Stein, Martin Palm, Gerhard SauthoffAbstract:Abstract Two-Phase Fe-rich Fe–Al–Zr alloys have been prepared consisting of binary Fe–Al with a very low solubility for Zr and the ternary Laves Phase Zr(Fe,Al) 2 or τ 1 Phase Zr(Fe,Al) 12 . Yield stress, flexural fracture strain, and oxidation behaviour of these alloys have been studied in the temperature range between room temperature and 1200 °C. Both the Laves Phase and the τ 1 Phase act as strengthening Phases increasing significantly the yield stress as well as the brittle-to-ductile transition temperature. Alloys containing disordered A2+ ordered D0 3 Fe–Al show strongly increased yield stresses compared to alloys with only A2 or D0 3 Fe–Al. The binary and ternary alloys with about 40at.% Al and 0 or 0.8at.% Zr show the effect of vacancy hardening at low temperatures which can be eliminated by heat treatments at 400 °C. At higher Zr contents this effect is lost and instead an increase of low-temperature strength is observed after the heat treatment. The increase of the high-temperature yield strength of Fe-40at.% Al by adding Zr is much stronger than by other ternary additions such as Ti, Nb, or Mo. Tests on the oxidation resistance at temperatures up to 1200 °C indicate a detrimental effect of Zr already for additions of 0.1at.%.
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structure and stability of Laves Phases part i critical assessment of factors controlling Laves Phase stability
Intermetallics, 2004Co-Authors: Frank Stein, Martin Palm, Gerhard SauthoffAbstract:Laves Phases form the largest group of intermetallic Phases. Although they are well known since long, there are still unsolved problems concerning the stability of the respective crystal structures. The Laves Phases crystallize with a cubic MgCu2- or a hexagonal MgZn2 -o r MgNi2-type structure which differ only by the particular stacking of the same four-layered structural units. It is still not possible to predict which of the structure types is the stable one for a Laves Phase compound AB2. Phase transformations from a cubic low-temperature structure to a hexagonal high-temperature structure were observed as well as stress-induced transformations from the hexagonal structure to the cubic one. In addition, deviations from the stoichiometric composition were reported to result in a change of the stable polytype in various systems. In this first of two consecutive papers dealing with fundamental aspects of the stability of Laves Phases, some factors which are known to affect the occurrence and structure type of Laves Phases are discussed and it is shown that, at least up to now, the existing models and calculations are not well suited to give a general description of the stability of Laves Phases. q 2004 Published by Elsevier Ltd.
Jean Nei - One of the best experts on this subject based on the ideXlab platform.
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annealing effects on Laves Phase related body centered cubic solid solution metal hydride alloys
Journal of Alloys and Compounds, 2016Co-Authors: K Young, Taihei Ouchi, Jean Nei, Lixin WangAbstract:Abstract Effects of thermal annealing (between 800 and 1100 °C) on the structural, gaseous Phase and electrochemical hydrogen storage properties of a Laves Phase-related body-centered-cubic (BCC) alloy, Ti15.6Zr2.1V40.0Cr11.2Mn6.9Co1.4Ni22.5Al0.3, were studied. Only BCC, TiNi, and C14 Phases appeared in the as-cast sample. Annealing at 800 and 900 °C increased the main hydrogen storage BCC Phase abundance and reduced C14 and TiNi catalytic Phases. Annealing at 1000 °C promoted the formation of Ti2Ni Phase. A σ-VNi Phase appeared after annealing at 1100 °C. In addition, the annealed samples also contained Zr and TiO2 debris. Electrochemical results suggested optimized annealing conditions of 900 °C for 12-h to optimize the storage capacity, high-rate performance, and activation due to a favorable balance in abundance between storage Phase (BCC) and catalytic Phases (C14 and TiNi).
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effects of cr zr v mn fe and co to the hydride properties of Laves Phase related body centered cubic solid solution alloys
Journal of Power Sources, 2015Co-Authors: K Young, Taihei Ouchi, Jean Nei, T MengAbstract:Abstract Chemical composition modifications of a Laves Phase-related BCC solid solution base alloy, Ti15.6Zr2.1V44Cr11.2Mn6.9Fe2.7Co1.4Ni15.7Al0.3, were investigated in order to study the function of each constituent element on the structural, gaseous Phase and electrochemical hydrogen storage properties of these alloys. In general, removal of Fe and decrease in V-content in exchange for higher Ni-content were found to improve both the electrochemical capacity and high-rate dischargeability, which are related to the decrease in C14-content and increase in TiNi-content. However, total elimination of the C14 Phase by removal of Zr resulted in a reduced discharge capacity, a prolonged activation period, and a less catalytic surface for electrochemical reaction. Besides the BCC and C14 Phases, the TiNi Phase was also found in every alloy in this study, contributing positively to the bulk diffusion of hydrogen while hindering the surface electrochemical reaction.
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structural hydrogen storage and electrochemical properties of Laves Phase related body centered cubic solid solution metal hydride alloys
International Journal of Hydrogen Energy, 2014Co-Authors: K Young, Jean Nei, Lixin Wang, D F WongAbstract:Abstract Structure, gaseous Phase hydrogen storage, and electrochemical properties of a series of Laves Phase-related BCC solid solution metal hydride alloys with BCC/C14 ratios ranging from 0.09 to 8.52 were studied. Some properties are correlated to the Phase abundance and V-content in the alloy with monotonic evolutions, for example, lattice constant, Phase abundance, and hydrogen storage pressure. Other properties such as gaseous Phase capacities, PCT hysteresis, high-rate dischargeability, and bulk hydrogen diffusion correlate better with the C14 Phase crystallite size, which are considered to be more related to the synergetic effect between main and secondary Phases. In contrast with conventional metal hydride alloys used in NiMH batteries, the electrochemical discharge capacities of these alloys are not between the maximum and the reversible hydrogen storage measured in the gaseous Phase. The current study's alloys have electrochemical capacities that are insensitive to composition but have much room for improvement, with high-rate dischargeabilities that are superior compared to other commercially available alloys. With further research, these alloys show potential for high-rate battery applications.