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

Kriegel, Mario J.; Kilmametov, Askar; Rudolph, Martin; Straumal, Boris B.; Горнакова, А. С.; Stöcker, Hartmut; Ivanisenko, Yulia; Fabrichnaya, Olga; Hahn, Horst; Rafaja, David

doi:10.1002/adem.201700933

Cited by 27 publications

(30 citation statements)

References 39 publications

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“…5 wt% Fe, it exceeded 10 wt% Fe at the interface between α‐Ti and β + ω. The comparison of the Fe concentration profile with the quality of ω diffraction spots confirms the former conclusions that the ω content increases as the Fe content approaches 4 wt% . In addition, this result is in accordance with conclusions from refs.…”

Section: Resultssupporting

confidence: 92%

“…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%

“…Consequently, for this composition the transformation of β → ω does not require mass transfer and thus just a small deformation (36° HPT rotation) is sufficient to transform β in this alloy almost completely to the ω phase. The studies of the thermal stability of HPT ω‐Ti(Fe) revealed the transformation sequence ω → α‐Ti(Fe) → α‐Ti + β → β upon heating . The DSC measurements performed in this work showed that the ω‐Ti(Fe) phase transformation to an Fe‐rich α‐Ti(Fe) phase is an exothermic process occurring at approx.…”

Section: Resultsmentioning

confidence: 61%

“…The smallest lattice mismatch between the β and ω lattices was found for an Fe content of approx. 4 wt% . Consequently, for this composition the transformation of β → ω does not require mass transfer and thus just a small deformation (36° HPT rotation) is sufficient to transform β in this alloy almost completely to the ω phase.…”

Section: Resultsmentioning

confidence: 91%

“…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%

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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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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

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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Microstructure Evolution and Phase Transformation of Ti‐1.0 wt%Fe Alloy with an Equiaxed α + β Initial Microstructure during High‐Pressure Torsion and Subsequent Annealing

2019

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Herein, the microstructure evolution and phase transformation during high‐pressure torsion (HPT) and subsequent annealing of Ti‐1.0 wt%Fe alloy with an equiaxed α + β initial microstructure are investigated. Both α and β grains in the initial microstructure fragment into smaller and elongated areas during HPT. X‐ray diffraction (XRD) analysis reveals that the deformation‐induced α to ω and β to ω phase transformations occur from the onset of HPT deformation. The β phase totally disappears after 1.5 rotations, whereas some α phase still remains even after 4 rotations. The nano‐hardness of β grains is much larger than that of α grains in the initial microstructure, due to the nano‐sized athermal ω precipitates inside the β grains. With an increase in the HPT rotation, the nano‐hardness of prior α areas continuously increases, whereas that of the prior β areas gradually decreases. During the subsequent annealing of HPT‐deformed sample, both ω to α and ω to β reverse‐phase transformations occur, and the deformation‐induced ω phase totally disappears at annealing temperatures above 400 °C. The recrystallization of α phase completes at an annealing temperature of 500 °C. At higher annealing temperatures, secondary α precipitates with ultrafine grain sizes start to appear inside the prior β areas.

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