The α→ω and β→ω phase transformations in Ti–Fe alloys under high-pressure torsion

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

doi:10.1016/j.actamat.2017.10.051

Cited by 133 publications

(115 citation statements)

References 86 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%

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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%

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

et al. 2018

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“…Hennig concluded from the ab initio calculations employing the density functional theory (DFT) that the alloying with β-stabilizer elements such as V, Mo, Fe, and Ta should lead to a decrease in the onset pressure of the α → ω transformation [7]. Recently, systematic studies of the HPT-induced ω-phase formation in Ti-Fe alloys revealed new possibilities for the experimental studies of the α → ω and β → ω transformations, facilitated by the combination of shear strain with high pressure [50,71].…”

Section: Discussionmentioning

confidence: 99%

“…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%

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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“…Recently, it has been reported that α → ω and β → ω phase transformations occurred for Ti-Fe alloys under high pressure deformation, and the mechanical properties might be improved after the high pressure phase transition [43,44]. Seen from Figure 9, two points are outside the strength-plasticity banana curve.…”

Section: Discussionmentioning

confidence: 93%

Fabrication of an Ultra-Fine Grained Pure Titanium with High Strength and Good Ductility via ECAP plus Cold Rolling

Jiang

Liu

et al. 2017

Metals

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Microstructure evolutions and mechanical properties of a commercially pure titanium (CP-Ti, grade 2) during multi-pass rotary-die equal-channel angular pressing (RD-ECAP) and cold rolling (CR) were systematically investigated in this work, to achieve comprehensive property for faster industrial applications. The obtained results showed that the grain size of CP-Ti decreased from 80 µm of as-received stage to 500 nm and 310 nm after four passes and eight passes of ECAP, respectively. Moreover, abundant dislocations were observed in ECAP samples. After subsequent cold rolling, the grain size of ECAPed CP-Ti was further refined to 120 nm and 90 nm, suggesting a good refining effect by combination of ECAP and CR. XRD (X-ray diffractometer) analysis and TEM (transmission electron microscope) observations indicated that the dislocation density increased remarkably after subsequent CR processing. Room temperature tensile tests showed that CP-Ti after ECAP + CR exhibited the best combination of strength and ductility, with ultimate tensile strength and fracture strain reaching 920 MPa and 20%. The high strength of this deformed CP-Ti originated mainly from refined grains and high density of dislocations, while the good ductility could be attributed to the improved homogeneity of UFG (ultra-fine grained) microstructure. Thus, a high strength and ductility ultra-fine grained CP-Ti was successfully prepared via ECAP plus CR.

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The α→ω and β→ω phase transformations in Ti–Fe alloys under high-pressure torsion

Cited by 133 publications

References 86 publications

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

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

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

Fabrication of an Ultra-Fine Grained Pure Titanium with High Strength and Good Ductility via ECAP plus Cold Rolling

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