Influence of β-Stabilizers on the α-Ti→ω-Ti Transformation in Ti-Based Alloys

Kilmametov, Askar; Горнакова, А. С.; Карпов, М. И.; Afonikova, N. S.; Korneva, Anna; Zięba, P.; Baretzky, B.; Straumal, Boris B.

doi:10.3390/pr8091135

Cited by 8 publications

(7 citation statements)

References 44 publications

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“…An increase of the annealing temperature up to 600 • C resulted in a decrease of the lattice parameters of the α-phase and, as a consequence, to a decrease of cell volume, which can be associated with the increase of niobium content in the cell (Table 2). These measurements are in a good agreement with a marked decrease in the values of the lattice parameters that took place in the Ti-based alloys doped with Fe, Cr, Ni and Co in the range of less than 1 wt.% [37]. After deformation, the cell volume of the α-phase in the alloys, preliminarily annealed at 600 • C, was lower than that in the alloys annealed at 450 • C. The increase of the cell volume may indicate a tendency towards HPT-induced niobium depletion of the α-matrix solid solution.…”

Section: Resultssupporting

confidence: 84%

Omega Phase Formation in Ti–3wt.%Nb Alloy Induced by High-Pressure Torsion

et al. 2021

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It is well known that severe plastic deformation not only leads to strong grain refinement and material strengthening but also can drive phase transformations. A study of the fundamentals of α → ω phase transformations induced by high-pressure torsion (HPT) in Ti–Nb-based alloys is presented in the current work. Before HPT, a Ti–3wt.%Nb alloy was annealed at two different temperatures in order to obtain the α-phase state with different amounts of niobium. X-ray diffraction analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for the characterisation of phase transitions and evolution of the microstructure. A small amount of the β-phase was found in the initial states, which completely transformed into the ω-phase during the HPT process. During HPT, strong grain refinement in the α-phase took place, as did partial transformation of the α- into the ω-phase. Therefore, two kinds of ω-phase, each with different chemical composition, were obtained after HPT. The first one was formed from the β-phase, enriched in Nb, and the second one from the α-phase. It was also found that the transformation of the α-phase into the ω-phase depended on the Nb concentration in the α-Ti phase. The less Nb there was in the α-phase, the more of the α-phase was transformed into the ω-phase.

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Section: Resultssupporting

confidence: 84%

Omega Phase Formation in Ti–3wt.%Nb Alloy Induced by High-Pressure Torsion

et al. 2021

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“…79) If one anneals the Ti4 wt.% Co alloy at different temperatures below T e , the amount of cobalt dissolved in ¡-phase increases with increasing temperature from 400 to 670°C. 61) The portion of ½ phase after HPT of these alloys decreased with increasing temperature from 400 to 670°C and thus with increasing cobalt content from 80% at 400°C to zero at 400 to 60°C (see red curve in Fig. 12).…”

Section: Hpt Of ¡+Intermetallic Alloysmentioning

confidence: 94%

“…In the following examples, the initial titanium alloys did not contain any ¡-phase before HPT treatment. 61,79,80,108) To do this, binary titanium alloys with various beta stabilizers were annealed below the temperature of the eutectoid transformation of the ¢ phase into a mixture of the ¡ phase and intermetallic compounds. Thus, prior to HPT, these alloys contained an ¡ solid solution of titanium with an alloying component and intermetallic phases (for example, TiFe, Ti 2 Co, Ti 2 Ni or TiCr 2 ).…”

Section: Hpt Of ¡+Intermetallic Alloysmentioning

confidence: 99%

Review - Phase Transitions in Ti Alloys Driven by the High Pressure Torsion

et al. 2023

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The high pressure torsion (HPT) of various binary Ti alloys with ¢-stabilizers (Fe, Co, Ni, Mo, Nb) was studied. Before HPT, the samples were annealed and contained (i) pure ¢-phase, (ii) ¡+¢ mixture with different portion of phases, (iii) ¡A or ¡AA martensites, (iv) the mixture of ¡-Ti and respective intermetallic phase. The microstructure of Ti alloys before and after HPT was studied by scanning and transmission electron microscopy (also high resolution one), X-rays diffraction (including the high-temperature in situ one), differential scanning calorimetry, atomic probe tomography, synchrotron irradiation. During HPT the (usual) strong grain refinement took place. Also, it was observed that HPT can lead to various phase transitions in the Ti alloys. In particular, the metastable high-pressure ½-phase and ¡A martensite can form. The composition of phases (similar to their grain size) reached the steady-state value after about 1.5 plunger revolutions. In some cases, the equifinality of the HPT-driven phase transitions was observed. Equifinality means that the composition and portion of phases after HPT do not depend on the composition and portion of phases before HPT.The HPT-driven phase transitions can be martensitic (i.e. without or almost without mass transfer) or diffusional (i.e. with mass transfer). In case of martensitic ¢-to-½ or ¡-to-½ phase transitions, the certain orientation relations between ¢ and ½ or ¡ and ½ phases were observed. The thermal stability of the ½-phase obtained by HPT has been studied by the in-situ X-rays diffraction at high temperatures. The ½-phase in the HPT-treated Ti alloys with ¢-stabilizers can remain in the samples up to 500600°C. It is much higher than in pure titanium (³180°C). Thus, the HPT-driven phase transitions open the new way for tailoring of grain size and phase composition of Ti-based alloys. In turn, it gives the new instrument in hands of engineers to improvement of the technologically important properties of Ti-based alloys. It is especially important for the medical application like the teeth or bone prosthesis.

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“…When the content of βstabilizing elements is low, the hcp martensite (α ) and orthorhombic martensite (α ) can be created from the β austenite phase by high-speed cooling [33]. Additionally, the hexagonal ω phase can be generated from the β phase via severe plastic deformation [34][35][36] and from the α phase under the drive of high-temperature torsion [33,35,[37][38][39][40]. The ω phase is detrimental to the shape memory effect and superelasticity of martensite.…”

Section: Introductionmentioning

confidence: 99%

Alloying Effect on Transformation Strain and Martensitic Transformation Temperature of Ti-Based Alloys from Ab Initio Calculations

Fang,

Xu,

Zhang

et al. 2023

Materials

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The accurate prediction of alloying effects on the martensitic transition temperature (Ms) is still a big challenge. To investigate the composition-dependent lattice deformation strain and the Ms upon the β to α″ phase transition, we calculate the total energies and transformation strains for two selected Ti−Nb−Al and Ti−Nb−Ta ternaries employing a first-principles method. The adopted approach accurately estimates the alloying effect on lattice strain and the Ms by comparing it with the available measurements. The largest elongation and the largest compression due to the lattice strain occur along ±[011]β and ±[100]β, respectively. As compared to the overestimation of the Ms from existing empirical relationships, an improved Ms estimation can be realized using our proposed empirical relation by associating the measured Ms with the energy difference between the β and α″ phases. There is a satisfactory agreement between the predicted and measured Ms, implying that the proposed empirical relation could accurately describe the coupling alloying effect on Ms. Both Al and Ta strongly decrease the Ms, which is in line with the available observations. A correlation between the Ms and elastic modulus, C44, is found, implying that elastic moduli may be regarded as a prefactor of composition-dependent Ms. This work sheds deep light on precisely and directly predicting the Ms of Ti-containing alloys from the first-principles method.

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Influence of β-Stabilizers on the α-Ti→ω-Ti Transformation in Ti-Based Alloys

Cited by 8 publications

References 44 publications

Omega Phase Formation in Ti–3wt.%Nb Alloy Induced by High-Pressure Torsion

Omega Phase Formation in Ti–3wt.%Nb Alloy Induced by High-Pressure Torsion

Review - Phase Transitions in Ti Alloys Driven by the High Pressure Torsion

Alloying Effect on Transformation Strain and Martensitic Transformation Temperature of Ti-Based Alloys from Ab Initio Calculations

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