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Open AccessFeature PaperArticle

Formation and Thermal Stability of ω-Ti(Fe) in α-Phase-Based Ti(Fe) Alloys

1
TU Bergakademie Freiberg, Institute of Materials Science, 09599 Freiberg, Germany
2
Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, 76344 Eggenstein-Leopoldshafen, Germany
3
Institute of Solid State Physics and Chernogolovka Scientific Center, Russian Academy of Sciences, 142432 Chernogolovka, Russia
4
Laboratory of Hybrid Nanomaterials, National University of Science and Technology “MISIS”, 119049 Moscow, Russia
*
Author to whom correspondence should be addressed.
Metals 2020, 10(3), 402; https://doi.org/10.3390/met10030402
Received: 4 March 2020 / Revised: 18 March 2020 / Accepted: 19 March 2020 / Published: 21 March 2020
In this work, the formation and thermal stability of the ω-Ti(Fe) phase that were produced by the high-pressure torsion (HPT) were studied in two-phase α-Ti + TiFe alloys containing 2 wt.%, 4 wt.% and 10 wt.% iron. The two-phase microstructure was achieved by annealing the alloys at 470 °C for 4000 h and then quenching them in water. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were utilized to characterize the samples. The thermal stability of the ω-Ti(Fe) phase was investigated using differential scanning calorimetry (DSC) and in situ high-temperature XRD. In the HPT process, the high-pressure ω-Ti(Fe) phase mainly formed from α-Ti. It started to decompose by a cascade of exothermic reactions already at temperatures of 130 °C. The decomposition was finished above ~320 °C. Upon further heating, the phase transformation proceeded via the formation of a supersaturated α-Ti(Fe) phase. Finally, the equilibrium phase assemblage was established at high temperatures. The eutectoid temperature and the phase transition temperatures measured in deformed and heat-treated samples are compared for the samples with different iron concentrations and for samples with different phase compositions prior to the HPT process. Thermodynamic calculations were carried out to predict stable and metastable phase assemblages after heat-treatments at low (α-Ti + TiFe) and high temperatures (α-Ti + β-(Ti,Fe), β-(Ti,Fe)). View Full-Text
Keywords: Ti–Fe; high-pressure torsion; microstructure; high-temperature XRD; differential scanning calorimetry; phase diagram; CalPhaD Ti–Fe; high-pressure torsion; microstructure; high-temperature XRD; differential scanning calorimetry; phase diagram; CalPhaD
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Kriegel, M.J.; Rudolph, M.; Kilmametov, A.; Straumal, B.B.; Ivanisenko, J.; Fabrichnaya, O.; Hahn, H.; Rafaja, D. Formation and Thermal Stability of ω-Ti(Fe) in α-Phase-Based Ti(Fe) Alloys. Metals 2020, 10, 402.

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