| 1. |
- Asokan, Vijayshankar, 1984, et al.
(författare)
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The influence of Si on the primary protection of lean FeCrAl model alloys in O2 and O2+H2O at 600 °C: A microstructural investigation
- 2021
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 179
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates the influence of Si on the high-temperature corrosion behavior of lean FeCrAl model alloys in O2 and O2+H2O at 600 °C. The addition of Si prevented breakaway oxidation in O2+H2O which may be explained by the increased Al-content and reduced Cr-content in the oxide (O2) as well as the Si-enrichment in the outer part of the scale (O2+H2O). A proposed explanation for the impact of Si-addition on the Cr- and Al-content was given by thermodynamic calculations which showed that the presence of Si increases the activity of Al in the alloy while reducing the activity of Cr.
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| 2. |
- Bigdeli, Sedigheh, 1984, et al.
(författare)
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Strategies for High-Temperature Corrosion Simulations of Fe-Based Alloys Using the Calphad Approach : Part I
- 2021
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Ingår i: Journal of Phase Equilibria and Diffusion. - : Springer Nature. - 1547-7037 .- 1863-7345. ; 42:3, s. 403-418
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Tidskriftsartikel (refereegranskat)abstract
- The environmental degradation of materials at high temperatures limits the useful life of different industrial components and hinders the development of more economical and environmentally friendly processes for the energy production. Despite the importance of this phenomena, a model to predict lifetime of materials that degrade due to high-temperature corrosion has up till now been lacking due to limitations of the computational possibilities and the complex nature of oxidation. In the present work we develop some strategies to model high-temperature corrosion in Fe-based alloys using the Calphad (Calculation of Phase Diagrams) approach. It is proposed that kinetic-based simulations for oxidation of Al and Cr can accurately represent the lifetime of the protective layers in FeCrAl and FeCr alloys at different temperatures in air. The oxide systems are in addition investigated by equilibrium calculations. The corrosion mechanisms of FeCr and FeCrAl alloys are discussed based on theoretical and experimental knowledge.
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| 3. |
- Eklund, Johan, 1991, et al.
(författare)
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High temperature corrosion behavior of FeCrAlSi model alloys in the presence of water vapor and KCl at 600 °C – The influence of Cr content
- 2022
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 198
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion behavior of Fe(5−20)Cr3Al2Si model alloys and the underlying mechanisms after breakaway oxidation was investigated at 600 °C. Rapid breakaway oxidation was triggered for all alloys in the presence of KCl(s). Thermogravimetric analysis showed that alloys with a Cr content of ≥ 10 wt% transitioned into sub-parabolic oxidation kinetics at an early stage of the oxidation process after breakaway oxidation. Through advanced electron/ion microscopy, this behavior was attributed to high Cr-enrichment in the bottom part of the inward-growing scale, indicating the formation of a healing layer. Additionally, alloys with elevated Cr-content (≥15 wt%) were more prone to grain boundary attack.
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| 4. |
- Eklund, Johan, 1991, et al.
(författare)
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Secondary corrosion protection of FeCr(Al) model alloys at 600 °C – The influence of Cr and Al after breakaway corrosion
- 2021
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 189
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Tidskriftsartikel (refereegranskat)abstract
- The influence of Cr and Al content on the oxidation behaviour of FeCr(Al) model alloys after breakaway oxidation at 600 °C and the underlying mechanisms were investigated in detail with thermogravimetrical analysis (TGA), thermodynamic calculations and advanced electron microscopy. The results showed that a Cr-content of ≥18 wt% drastically reduced the growth rate of the Fe-rich oxide scale, formed after breakaway oxidation, for FeCrAl alloys but not for FeCr alloys. This was attributed to the ability of the Fe(18-25)CrAl alloys to prevent internal oxidation, which enables the formation of a healing layer.
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| 5. |
- Esmaily, Mohsen, et al.
(författare)
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High-temperature oxidation behaviour of AlxFeCrCoNi and AlTiVCr compositionally complex alloys
- 2020
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Ingår i: npj Materials Degradation. - : Springer Science and Business Media LLC. - 2397-2106. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Compositionally complex alloys (CCAs), also termed as high entropy alloys (HEAs) or multi-principal element alloys (MPEAs), are being considered as a potential solution for many energy-related applications comprising extreme environments and temperatures. Herein, a review of the pertinent literature is performed in conjunction with original works characterising the oxidation behaviour of two diverse Al-containing alloys; namely a lightweight (5.06 g/cm(3)) single-phase AlTiVCr CCA and a multiple-phase Al0.9FeCrCoNi CCA (6.9 g/cm(3)). The thermogravimetric results obtained during oxidation of the alloys at 700 and 900 degrees C revealed that both alloys tended to obey the desired parabolic rate law. Post-exposure analysis by means of electron microscopy indicated that while the oxide scale formed on the AlTiVCr is adherent to the substrate, the scale developed on the Al0.9FeCrCoNi displays a notable spalling propensity. This study highlights the need for tailoring the protective properties of the oxide scale formed on the surface of the CCAs.
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| 6. |
- Gunasekara, Saman Nimali, 1982-, et al.
(författare)
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Thermodynamic Assessment of Binary Erythritol-Xylitol Phase Diagram for Phase Change Materials Design
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Here, the experimental phase equilibrium data of the erythritol-xylitol system were thermodynamically optimized, to explore compositions suitable as phase change materials (PCMs) for thermal energy storage (TES). A previous experimental study revealed that erythritol-xylitol was a partially isomorphous system with a eutectic. In the thermodynamic evaluation, the CALPHAD method was employed coupling the phase diagram and thermodynamic property information. There, both unary and binary systems’ experimental data were taken into account, and all phases were described using the substitutional solution model. Finally, a self-consistent thermodynamic description for the erythritol-xylitol system was achieved. The calculated eutectic point is at 76.7 °C and 26.8 mol% erythritol, agreeing well with the experimental data. The calculated phase diagram better-verifies the systems’ solidus and the solvus, disclosing the stable phase relations. Based on the Gibbs energy minimization, phase diagrams can be predicted for the binary and higher order systems, provided the component subsystems are thermodynamically assessed beforehand. In conclusion, to move forward beyond e.g. non-isomorphous simple eutectic systems, methods using Gibbs free energy minimization from a fundamental point-of-view such as CALPHAD are essential.
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| 7. |
- Sundman, Bo, et al.
(författare)
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A method for handling the extrapolation of solid crystalline phases to temperatures far above their melting point
- 2020
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Ingår i: Calphad. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0364-5916 .- 1873-2984. ; 68
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Tidskriftsartikel (refereegranskat)abstract
- Thermodynamic descriptions in databases for applications in computational thermodynamics require representation of the Gibbs energy of stable as well as metastable phases of the pure elements as a basis to model multicomponent systems. In the Calphad methodology these representations are usually based on physical models. Reasonable behavior of the thermodynamic properties of phases extrapolated far outside their stable ranges is necessary in order to avoid that they become stable just because these properties extrapolate badly. This paper proposes a method to prevent crystalline solid phases in multi-component systems to become stable again when extrapolated to temperatures far above their melting temperature.
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