| 1. |
- Hertzman, S., et al.
(författare)
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Nitrogen Solubility in Alloy Systems Relevant to Stainless Steels
- 2021
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Nature. - 1073-5623 .- 1543-1940. ; 52:9, s. 3811-3820
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Tidskriftsartikel (refereegranskat)abstract
- High-performance stainless steels are alloyed with nitrogen for several different reasons. For the austenitic grades, the kinetics of deleterious phase transformations are delayed, the strength is increased, and the corrosion resistance is improved. For duplex steels, the weldability and corrosion resistance depend directly on their nitrogen contents. Reliable databases are crucial for the development of new stainless steels and their processing. In order to calibrate the existing thermodynamic data, a series of experiments was undertaken. Several laboratory alloys in Fe–Cr–X systems, where X = Ni, Mn, Cu, were reacted with nitrogen gas at nitrogen activities 0.5 and 1 in the temperature range from 1050 °C to 1350 °C and subsequently analyzed for nitrogen solubility and phase constitution. A novel, simplified experimental technique was used, providing a dew point that is low enough to allow for fast nitrogen transport through the specimen surface, ensuring equilibrium conditions. The results are compared to thermodynamic equilibrium calculations.
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| 2. |
- Lu, Song, et al.
(författare)
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Stacking fault energy of C-alloyed steels : The effect of magnetism
- 2017
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 122, s. 72-81
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations have been performed to study the effect of C on the stacking fault energy (SFE) of paramagnetic γ-Fe and Fe[sbnd]Cr[sbnd]Ni austenitic steel. In these systems, the local magnetic structure is very sensitive to the volume in both fcc and hcp structures, which emphasizes the importance of the magnetovolume coupling effect on the SFE. The presence of C atom suppresses the local magnetic moments of Fe atoms in the first coordination shell of C. Compared to the hypothetical nonmagnetic case, paramagnetism significantly reduces the effect of C on the SFE. In the scenario of C being depleted from the stacking fault structure or twin boundaries, e.g., due to elevated temperature, where the chemical effect of C is dissipated, we calculate the C-induced volume expansion effect on the SFE. The volume induced change in the SFE corresponds to more than ∼ 50% of the total C effect on the SFE obtained assuming uniform C distribution.
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| 3. |
- Smeds, K., et al.
(författare)
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Objective measures to quantify the perceptual effects of noise reduction in hearing aids
- 2011
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Ingår i: Proceedings of the AES International Conference. ; , s. 101-108
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Konferensbidrag (refereegranskat)abstract
- Twenty listeners with hearing impairment evaluated three noise-reduction algorithms using paired comparisons of speech clarity, noise loudness, and preference. The subjective test produces results in terms of physical signal-to-noise ratios that correspond to equal subjective performance with and without the noise-reduction algorithms. This facilitates a direct test of how well a number of objective performance measures correspond with the subjective test results.
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| 4. |
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| 5. |
- Hertzman, S., et al.
(författare)
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A Thermodynamic analysis of the Fe-Cr-N system
- 1987
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Ingår i: Metallurgical Transactions A. ; 18:10, s. 1745-1752
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Tidskriftsartikel (refereegranskat)abstract
- New experimental information on the phase relations in the Fe-Cr-N system at 1273 K is presented. Together with previous information it is used in a thermodynamic analysis of the system in the temperature range from 1273 to 1473 K. A set of parameter values is derived which defines the Gibbs energy of the individual phases and allows the phase diagram to be calculated. Satisfactory agreement with experimental information is obtained. © 1987 The Metallurgical of Society of AIME.
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| 6. |
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| 7. |
- Pettersson, N., et al.
(författare)
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Nanostructure evolution and mechanical property changes during aging of a super duplex stainless steel at 300°C
- 2015
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Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 647, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- The nanostructure evolution and the corresponding changes in mechanical properties of a super duplex stainless steel 2507 (UNS S32750) during aging at 300. °C up to 12,000. h have been investigated. Microstructural studies using transmission electron microscopy and atom probe tomography show that subtle Cr concentration fluctuations develop during aging. The amplitude of the concentration fluctuations is proportional to the hardness of the ferrite phase, and it is also proportional to the decrease in room temperature impact toughness during aging. The fracture behaviour of the alloy changes gradually from ductile to cleavage fracture, upon aging. The cracks were found to propagate through the ferrite phase, partly along deformation twin interfaces, and delamination between the austenite and ferrite phases was observed.
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| 8. |
- Wessman, Sten, et al.
(författare)
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On Phase Equilibria in Duplex Stainless Steels
- 2010
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Ingår i: STEEL RES INT. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:5, s. 337-346
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium conditions of four duplex stainless steels; Fe-23Cr-4.5Ni-0.1N, Fe-22Cr-5.5Ni-3Mo-0.17N, Fe-25Cr-7Ni-4Mo-0.27N and Fe-25Cr-7Ni-4Mo-1W-1.5Cu-0.27N were studied in the temperature region from 700 to 1000 degrees C. Phase compositions were determined with SEM EDS and the phase fractions using image analysis on backscattered SEM images. The results showed that below 1000 degrees C the steels develop an inverse duplex structure with austenite and sigma phase, of which the former is the matrix phase. With decreasing temperature, the microstructure will be more and more complex and finely dispersed. The ferrite is, for the higher alloyed steels, only stable above 1000 degrees C and at lower temperatures disappears in favour of intermetallic phases. The major intermetallic phase is sigma phase with small amounts of chi phase, the latter primarily in high Mo and W grades. Nitrides, not a focus in this investigation, were present as rounded particles and acicular precipitates at lower temperatures. The results were compared to theoretical predictions using the TCFE5 and TCFE6 databases.
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| 9. |
- Wessman, Sten, et al.
(författare)
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On the effect of nickel substitution in duplex stainless steel
- 2008
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Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847. ; 24:3, s. 348-355
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Tidskriftsartikel (refereegranskat)abstract
- The present experimental and theoretical study investigates the effect of nickel on the phase balance and resulting properties of a 22Cr duplex stainless steel. The decrease in nickel was balanced by nitrogen and manganese additions. It was found that a minimum nickel content was required to maintain mechanical and corrosion properties at technically relevant levels. The influence of increasing nitrogen content on resulting phase composition and properties is discussed.
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| 10. |
- Zhou, J., et al.
(författare)
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A study of duplex stainless steels aged at 325°C under applied tensile load
- 2011
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Ingår i: 7th European Stainless Steel Conference: Science and Market; Como; Italy; 21 September 2011 through 23 September 2011. - : Associazione Italiana di Metallurgia. - 9788885298842
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Konferensbidrag (refereegranskat)abstract
- Duplex stainless steels (DSS) are widely used due to their good combination of corrosion resistance and mechanical properties. The embrittlement caused by phase separation of ferrite in DSS, however, limits the maximum service temperature. Since weldments have been considered most sensitive it has been speculated whether weld residual stresses contribute to the kinetics of phase separation. A mechanistic study was performed on commercial DSS materials of different alloying levels. Specimens were aged under load and the mechanical properties in terms of hardness and impact toughness were determined. Also weld structures and simulated HAZ structures were tested. Differences in response were observed for the different microstructures, which were characterized by EBSD and TEM. The decomposition was characterized using atom probe tomography and the results seem to support the effect of stress on kinetics.
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