| 1. |
- De Colle, Mattia, et al.
(författare)
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Study of the Hydration Behavior of Synthetic Ferropericlase with LowIron Oxide Concentrations to Prevent Swelling in Steel Slags
- 2021
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Ingår i: Journal of Sustainable Metallurgy. - : Springer Nature. - 2199-3831 .- 2199-3823.
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Tidskriftsartikel (refereegranskat)abstract
- Steel slags generally swell when subjected to water or humidity, which prevents proper recycling in the cement or asphaltindustries. The MgO and CaO phases in steel slags are responsible for this phenomenon, as both minerals easily absorb waterto form their respective hydroxides. MgO is often present in steel slags in a solid solution with several oxides, constitutingthe so-called RO phase. This study investigates the hydration rate of an RO phase consisting of FeO and MgO called ferropericlase.The material was synthesized in a laboratory furnace by sintering a FeO–MgO powder mixture with varying initialFeO contents (approximately 10, 15, and 20 wt%). Thereafter, electron probe micro-analyzer (EPMA) and X-ray diffraction(XRD) spectroscopies were used to characterize the structure of the samples, which were mainly composed of ferropericlaseand an exsolution of magnesioferrite. Also, Mössbauer spectra showed that the total ferrous iron proportion (Fe2+/ΣFe) ofthe sintered samples was in the range of 0.55–0.72. To measure the hydration behavior, the samples in powder form werecured in an autoclave at an H2Opartial pressure of 2 atm. Thereafter, thermal gravimetric analysis (TGA) was performed tomeasure the amount of water absorbed during the autoclave curing from the mass drop associated with the dehydration ofthe hydroxide. The study found a linear correlation between the initial FeO content and the weight loss after TGA, with areduction down to 6% in the sample with an initial FeO content of 20 wt% content compared to pure MgO.
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| 2. |
- Wang, Wei, et al.
(författare)
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In-situ real time observation of martensite transformation in duplex fcc+hcp cobalt based entropic alloys
- 2020
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Ingår i: Materialia. - : Elsevier BV. - 2589-1529. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Athermal martensite transformation in duplex fcc+hcp Co-based entropic alloys during continuous cooling was investigated in-situ. The real time observation was carried out using high temperature confocal laser scanning microscopy (HT-CLSM). This technique enables the detection of the athermal fcc to hcp transformation in entropic alloys, which is not sensitively detected by conventional thermomechanical methods e.g. dilatometer. The martensite fraction increases with increasing martensite starting temperature, and vice versa. Meanwhile, the martensite starting temperature decreases with the increasing grain size. In addition, the morphology and nucleation sites for martensite formation is discussed. This is the first time the that HT-CLSM technique is utilized in the field of entropic alloys. This in-situ observation technique coupled with thermodynamic calculations may help in the design of entropic alloys through the tailoring of the desired microstructure.
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| 3. |
- Wang, Wei, et al.
(författare)
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Inclusion engineering in Co-based duplex entropic alloys
- 2021
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 210
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Tidskriftsartikel (refereegranskat)abstract
- Co-based duplex entropic alloy is designed very recently to replace pure Co as a major component of the binder phase for cemented carbide cutting tools. This work aims to provide a fundamental study of oxide inclusion characteristics in the duplex fcc + hcp Co-based entropic alloys. It is found that the Co85-xCrxFe7.5Ni7.5 (x = 15, 30 at.%) alloys hold the highest liquidus (T-liq) and solidus (T-sol) temperatures, compare with the Co85-xCrxMn7.5Ni7.5 (x = 15, 30 at.%) and Co77.5-xCrxFe7.5Mn7.5Ni7.5 (x = 15, 30 at.%) alloys. For each grade, the increasing Cr content leads to a decrease of T-sol and T-liq temperatures. It is also noted that there is an approximate 100 degrees C of undercooling exists in each grade during the solidification. The stable oxide inclusion in the Co85-xCrxMn7.5Ni7.5 and Co77.5-xCrxFe7.5Mn7.5Ni7.5 alloys is the MnCr2O4 type, while Cr2O3 is the main stable inclusion in the Co85-xCrxFe7.5Ni7.5 alloy. Furthermore, the size range of the MnCr2O4 particles is larger than that of Cr2O3. The theoretical calculation shows that MnCr2O4 has a higher coagulation coefficient than Cr2O3 does. This is due to the influence of the thermo-physical parameters, i.e. the interfacial energy between the oxide and the alloy and the viscosity of liquid alloy. The theoretical calculation fits well with the experimental findings.
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| 4. |
- Wang, Yong, et al.
(författare)
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Combination of In Situ Confocal Microscopy and Calorimetry to Investigate Solidification of Super- and Hyper-Duplex Stainless Steels
- 2023
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 94:11
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Tidskriftsartikel (refereegranskat)abstract
- The solidification processes of super- and hyper-duplex stainless steels (i.e., UNS S32750 and S 33 207) are investigated in situ by a high-temperature confocal laser scanning microscope (HT-CLSM) and differential scanning calorimetry (DSC). The variations of δ-ferrite phase fraction during solidification are measured quantitatively. The results show that liquid L→δ-ferrite transformation first occurs at a certain degree of supercooling during the solidification process of steel. UNS S3DSS 3207 with a higher Cr content can result in a higher nucleation temperature and faster growth of δ-ferrite compared to those of UNS S332750 steel. Moreover, both the liquidus (TL) and solidus temperatures (TS) are increased with the increasing Cr content, while TL increases greater than TS. Electron microscopies are used to quantify the fraction and composition of each phase. Scheil equation is employed to predict the distribution behavior of the main alloying elements in the solidification process, and the predicted results are consistent with the experimental findings. This study aims to provide real-time experimental insights into the solidification kinetics of state-of-the-art high-alloy-grade duplex steels and benefits for controlling the casting process in the real production of stainless steels.
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| 5. |
- Xuan, Changji, et al.
(författare)
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Wettability of Al2O3, MgO and Ti2O3 by Liquid Iron and Steel
- 2015
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Ingår i: ISIJ International. - 0915-1559 .- 1347-5460. ; 55:9, s. 1882-1890
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Tidskriftsartikel (refereegranskat)abstract
- The wetting behavior of liquid iron and steel on Al2O3, MgO and Ti2O3 substrates was measured by using the sessile drop method. Measurements were carried out using a controlled oxygen partial pressure and using an argon protected atmosphere. For the Al2O3 and MgO substrates, reaction layers in form of FeAl2O4 and MgO-FeO (solid solution) were formed. These layers slightly decreased the contact angle and surface tension values after a full melting. For a Ti2O3 substrate in contact with pure Fe, no-reaction could be observed at the interface. Furthermore, the contact angle and surface tension values were almost stable after a full melting. For a Ti2O3 substrate in contact with steel, the contact angle and surface tension values decreased steeply after a full melting, due to the formation Al2TiO5 reaction layer formation at the interface.
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