Evidence of α → ω phase transition in titanium after high pressure torsion

2008 ◽  
Vol 99 (1) ◽  
pp. 36-41 ◽  
Author(s):  
Yulia Ivanisenko ◽  
Askar Kilmametov ◽  
Harald Rösner ◽  
Ruslan Z. Valiev
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Ω Phase

X-Ray Analysis of High Pressure Torsion Induced Nanostructures in Ti and Ni

2006 ◽  
Vol 114 ◽  
pp. 329-336 ◽  
Author(s):  
A.R. Kilmametov ◽  
Ruslan Valiev ◽  
Igor V. Alexandrov
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Orientation Distribution ◽  
Nanocrystalline State ◽  
Cubic Symmetry ◽  
X Ray ◽  
Ω Phase ◽  
Commercially Pure ◽  
Pressure Phase

X-ray investigations revealed that the increase in the applied pressure during high pressure torsion (HPT) of commercially pure Ti leads not only to substructure refinement with an increase of the dislocation density and microstrain level but also to an α→ ω phase transition at room temperature. The coexistence of both α and ω phases, the latter known as a high pressure phase, in the ratio approximately of 1:3 has been obtained after removal of thehigh pressure. Texture analysis of electodeposited Ni after HPT discovered a new form of crystallite orientation distribution in the nanocrystalline state. A nearly random orientation crystallite distribution has been observed unlike the “traditional” case of a shear texture forming in cubic symmetry metals. The crystallographic texture data obtained were considered as experimental evidence of the changed plastic deformation mechanisms in nanocrystalline Ni produced by HPT.

scholarly journals Slippage during high-pressure torsion of commercially pure titanium and application of accumulative HPT to it

2022 ◽  
Vol 1213 (1) ◽  
pp. 012003
Author(s):  
D V Gunderov ◽  
A A Churakova ◽  
A V Sharafutdinov ◽  
V D Sitdikov ◽  
V V Astanin
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Pure Titanium ◽  
Phase Changes ◽  
Phase Content ◽  
Commercially Pure Titanium ◽  
Micro Hardness ◽  
Ω Phase ◽  
Commercially Pure ◽  
First Time

Abstract A new efficient method was used to find that in the case of high-pressure torsion of commercially pure titanium, accumulation of shear strain in Ti does not occur due to slippage of anvils. Despite this, micro-hardness increases as the number of turns n increases, and Ti structure is refined more intensively. High-pressure torsion is accompanied by a high-pressure ω-phase formation. However, the content of ω-phase changes non-monotonously with an increase in the number of turns. First, while number of turns is less than n=5, the ω-phase content reaches 50%. Upon further deformation, the ω-phase content decreases to 15% for n=20. A new accumulative high-pressure torsion method is applied to commercially pure titanium for the first time. Accumulative high-pressure torsion leads to the strongest transformation of the structure and an increase in hardness, since stronger real deformation occurs due to composition of compression and torsion strain cycles.

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

2018 ◽  
Vol 144 ◽  
pp. 337-351 ◽  
Author(s):  
A.R. Kilmametov ◽  
Yu. Ivanisenko ◽  
A.A. Mazilkin ◽  
B.B. Straumal ◽  
A.S. Gornakova ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformations ◽  
High Pressure Torsion ◽  
Ω Phase ◽  
Fe Alloys

Phase transformation kinetics of ω-phase in pure Ti formed by high-pressure torsion

2015 ◽  
Vol 51 (5) ◽  
pp. 2608-2615 ◽  
Author(s):  
Nozomu Adachi ◽  
Yoshikazu Todaka ◽  
Kenshu Irie ◽  
Minoru Umemoto
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
High Pressure Torsion ◽  
Transformation Kinetics ◽  
Ω Phase ◽  
Phase Transformation Kinetics ◽  
Kinetics Of

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

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2262
Author(s):  
Anna Korneva ◽  
Boris Straumal ◽  
Askar Kilmametov ◽  
Alena Gornakova ◽  
Anna Wierzbicka-Miernik ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Phase Transformations ◽  
Grain Refinement ◽  
High Pressure Torsion ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Transmission Electron ◽  
Different Temperatures

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.

Thermal stability and microhardness of metastable ω-phase in the Ti-3.3 at.% Co alloy subjected to high pressure torsion

2020 ◽  
Vol 834 ◽  
pp. 155132 ◽  
Author(s):  
Anna Korneva ◽  
Boris Straumal ◽  
Askar Kilmametov ◽  
Łukasz Gondek ◽  
Anna Wierzbicka-Miernik ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Ω Phase

The α↔ω phase transformations and thermal stability of Ti Co alloy treated by high pressure torsion

2021 ◽  
Vol 173 ◽  
pp. 110937
Author(s):  
A. Korneva ◽  
B.B. Straumal ◽  
A.R. Kilmametov ◽  
Ł. Gondek ◽  
A. Wierzbicka-Miernik ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
Phase Transformations ◽  
High Pressure Torsion ◽  
Ω Phase ◽  
Thermal Stability Of

scholarly journals Influence of HPT and Accumulative High-Pressure Torsion on the Structure and Hv of a Zirconium Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 573
Author(s):  
Dmitry Gunderov ◽  
Andrey Stotskiy ◽  
Yuri Lebedev ◽  
Veta Mukaeva
Keyword(s):  
High Pressure ◽  
Zirconium Alloy ◽  
High Pressure Torsion ◽  
Ti Alloy ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ω Phase ◽  
First Time ◽  
Torsion Deformation

The authors previously used the accumulative high-pressure torsion (ACC HPT) method for the first time on steel 316, β-Ti alloy, and bulk metallic glass vit105. On low-alloyed alloys, in particular, the zirconium alloy Zr-1%Nb, the new method was not used. This alloy has a tendency to α → ω phase transformations at using simple HPT. When using ACC HPT, the α → ω transformation can be influenced to a greater extent. This article studies the sliding effect and accumulation of shear strain in Zr-1%Nb alloy at various stages of high-pressure torsion (HPT). The degree of shear deformation at different stages of HPT was estimated. The influence of various high-pressure torsion conditions on the micro-hardness and phase composition by X-ray diffraction (XRD) of Zr-1%Nb was analyzed. It is shown that at high-pressure torsion revolutions of n = 2, anvils and the specimen significantly slip, which is a result of material strengthening. It was found that despite sliding, regular high-pressure torsion resulted in the high strengthening of Zr-1%Nb alloy (micro-hardness more than doubled), and after high-pressure torsion n = 10, up to 97% of the high-pressure ω-phase was formed in it (as in papers of other researchers). Accumulative high-pressure torsion deformation leads to the strongest transformation of the Zr-1%Nb structure and Hv and, therefore, to a higher real strain of the material due to composition by upsetting and torsion in strain cycles.

In Situ Observation of the Phase Transformations in Ti15Mo Alloy Deformed by High Pressure Torsion

2018 ◽  
Vol 385 ◽  
pp. 206-211
Author(s):  
Miloš Janeček ◽  
Kristina Bartha ◽  
Josef Stráský ◽  
Jozef Veselý ◽  
Veronika Polyakova ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformations ◽  
High Pressure Torsion ◽  
Solution Treatment ◽  
Thin Foil ◽  
Scanning Calorimetry ◽  
Β Phase ◽  
Ω Phase ◽  
In Situ Heating

Metastable β-Ti alloys including Ti15Mo alloy are perspective candidates for use in medical applications. During thermal treatment Ti15Mo alloy undergoes various phase transformations. After solution treatment it contains metastable β-phase and ω-phase. During annealing the ω-phase partially dissolves as well as stable α-phase particles are formed. The solution treated Ti15Mo alloy was deformed by high pressure torsion (HPT) at room temperature. Significant grain refinement with grain size of ~100 nm was achieved even after 1/4 of HPT rotation. The effect of the ultra-fine grained (UFG) structure achieved by HPT on the phase transformations was studied by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) during in-situ heating. High density of lattice defects, dense network of grain boundaries as well as ongoing recovery and recrystallization upon heating significantly affected the phase transitions. Observation of the microstructure during in-situ heating in TEM revealed no representative changes in transparent part of the sample due to the “thin foil effect”.

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