Phase Transformations in Ti–Fe Alloys Induced by High‐Pressure Torsion

Straumal, Boris B.; Kilmametov, Askar; Ivanisenko, Yulia; Горнакова, А. С.; Mazilkin, Andrey; Kriegel, Mario J.; Fabrichnaya, Olga; Baretzky, B.; Hahn, Horst

doi:10.1002/adem.201500143

Cited by 101 publications

(37 citation statements)

References 33 publications

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“…The torsion torque increased during 1-2 anvil rotations in all alloys and pure Ti and then remained almost unchanged. In other words, it reached a steady state, as was observed previously in other alloys [16][17][18][19][20]51,52]). The central part (about 3 mm in diameter) of each disk after HPT was excluded from further investigations (since it is low-deformed).…”

Section: Methodssupporting

confidence: 83%

“…A number of SPD techniques include the application of high pressure, especially the high pressure torsion (HPT) one. It is known that the combination of shear strain with high pressure (i.e., in case of HPT) decreases the onset of the α → ω transition in comparison with quasi-hydrostatic conditions [2,[49][50][51]. The goal of this work is to study how the Co addition to Ti influences formation of the ω-phase under HPT.…”

Section: Introductionmentioning

confidence: 99%

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The α → ω Transformation in Titanium-Cobalt Alloys under High-Pressure Torsion

Kilmametov

Ivanisenko

Straumal

et al. 2017

Metals

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Abstract:The pressure influence on the α → ω transformation in Ti-Co alloys has been studied during high pressure torsion (HPT). The α → ω allotropic transformation takes place at high pressures in titanium, zirconium and hafnium as well as in their alloys. The transition pressure, the ability of high pressure ω-phase to retain after pressure release, and the pressure interval where α and ω phases coexist depend on the conditions of high-pressure treatment. During HPT in Bridgeman anvils, the high pressure is combined with shear strain. The presence of shear strain as well as Co addition to Ti decreases the onset of the α → ω transition from 10.5 GPa (under quasi-hydrostatic conditions) to about 3.5 GPa. The portion of ω-phase after HPT at 7 GPa increases in the following sequence: pure Ti → Ti-2 wt % Co → Ti-4 wt % Co → Ti-4 wt % Fe.

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Section: Methodssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

The α → ω Transformation in Titanium-Cobalt Alloys under High-Pressure Torsion

Kilmametov

Ivanisenko

Straumal

et al. 2017

Metals

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“…Recently, several works investigated the phase transformations in the Ti–Fe system being induced by a high‐pressure torsion process (HPT) and the thermal stability of the pressure induced phases . The comparison of these findings with the results of the present work shows very interesting similarities in the transformation pathway upon heating, which will be discussed in the following.…”

Section: Resultssupporting

confidence: 67%

“…In these works, it was shown that the transformation of α′ and β to the high‐pressure ω phase strongly depends on the iron composition. The smallest lattice mismatch between the β and ω lattices was found for an Fe content of approx.…”

Section: Resultsmentioning

confidence: 99%

“…Only very little is known about the high‐temperature stability of metastable phases, which are produced by quenching of Ti–Fe alloys. The stability of these phases (after water quenching) was investigated for only two alloy compositions (1 and 10 wt% Fe) by means of the thermal analysis upon heating . The presence of exothermal events in the differential scanning calorimetry (DSC) curves indicated several phase transformations, but the correlation of the phase transformations with the microstructure changes was not described yet.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Stability of Athermal ω‐Ti(Fe) Produced upon Quenching of β‐Ti(Fe)

et al. 2018

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This work shows the formation of the athermal ω phase in alloy Ti-4 wt% Fe. The alloy under study, heat treated at 800 C for 100 h and subsequently water quenched, is investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The thermal stability of ω-Ti(Fe) is investigated by differential scanning calorimetry (DSC). The DSC measurements show a cascade of several thermic events between 160 and 450 C, and one strong and sharp exothermic DSC peak at $480 C. The phase transformations and other microstructural changes behind these events are explained by complementary use of XRD, electron backscatter diffraction (EBSD), and TEM analyses that are performed on samples heated stepwise in the DSC apparatus. These experiments indicate that the embryos of athermal ω-Ti(Fe) grow up to $400 C and start to decompose into an α-Ti(Fe) þ β assemblage already at 450 C. At $480 C, the decomposition of the athermal ω-Ti(Fe) phase is practically finished. Thermal stability of athermal ω-Ti(Fe) is compared with the thermal stability of ω-Ti(Fe) produced in a high-pressure torsion (HPT) process, indicating a higher thermal stability of ω-Ti(Fe) in the non-deformed alloys.

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Transformation Pathway upon Heating of Ti–Fe Alloys Deformed by High‐Pressure Torsion

et al. 2018

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The current work presents the results of a study of the thermal stability of metastable ω-Ti(Fe) produced by a high-pressure torsion process and describes the phase transformations of ω-Ti(Fe) upon heating. The titanium alloys under study contain between 1 and 7 wt% of iron, the phase transitions are investigated using a combination of in situ high-temperature X-ray diffraction and differential scanning calorimetry. The high-temperature X-ray diffraction reveals the phase sequence ω ! α' ! α þ β ! β upon heating. The differential scanning calorimetry shows that the first phase transformation is exothermal and that the temperature of this phase transition is independent of the iron concentration within the composition range under study. Subsequent phase transitions are endothermal and the respective transition temperatures depend on the iron concentration. The differences between the phase stabilities conclude from the phase diagram and the phase stabilities observe experimentally are explained by the partial coherence of the α/α 0 -Ti and β-Ti grains.

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Phase Transformations in Ti–Fe Alloys Induced by High‐Pressure Torsion

Cited by 101 publications

References 33 publications

The α → ω Transformation in Titanium-Cobalt Alloys under High-Pressure Torsion

The α → ω Transformation in Titanium-Cobalt Alloys under High-Pressure Torsion

Thermal Stability of Athermal ω‐Ti(Fe) Produced upon Quenching of β‐Ti(Fe)

Transformation Pathway upon Heating of Ti–Fe Alloys Deformed by High‐Pressure Torsion

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