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.

scholarly journals The Phase Transformations Induced by High-Pressure Torsion in Ti–Nb-Based Alloys

2021 ◽  
pp. 1-7
Author(s):  
Anna Korneva ◽  
Boris Straumal ◽  
Askar Kilmametov ◽  
Lidia Lityńska-Dobrzyńska ◽  
Robert Chulist ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Phase Transformations ◽  
High Pressure Torsion ◽  
Chemical Compositions ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Nb Content ◽  
Long Time

The study of the fundamentals of the α → ω and β → ω phase transformations induced by high-pressure torsion (HPT) in Ti–Nb-based alloys is presented in the current work. Prior to HPT, three alloys with 5, 10, and 20 wt% of Nb were annealed in the temperature range of 700–540°C in order to obtain the (α + β)-phase state with a different amount of the β-phase. The samples were annealed for a long time in order to reach equilibrium Nb content in the α-solid solution. Scanning electron microscope (SEM), transmission electron microscopy, and X-ray diffraction techniques were used for the characterization of the microstructure evolution and phase transformations. HPT results in a strong grain refinement of the microstructure, a partial transformation of the α-phase into the ω-phase, and a complete β → ω phase transformation. Two kinds of the ω-phase with different chemical compositions were observed after HPT. The first one was formed from the β-phase, enriched in Nb, and the second one from the almost Nb-pure α-phase. It was found that the α → ω phase transformation depends on the Nb content in the initial α-Ti phase. The less the amount of Nb in the α-phase, the more the amount of the α-phase is transformed into the ω-phase.

Phase Transformation in Binary Titanium-Base Alloys with Metals of the I, IV−VIII Groups

2007 ◽  
Vol 546-549 ◽  
pp. 1349-1354 ◽  
Author(s):  
A.V. Dobromyslov
Keyword(s):  
Electron Microscopy ◽  
Structural Information ◽  
Eutectoid Decomposition ◽  
X Ray Diffraction ◽  
Minimum Concentration ◽  
X Ray ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Transmission Electron

Martensitic β→α′(α″) transformation, β→ω transformation and eutectoid decomposition in a series of Ti-base alloys with d transition metals of Groups I, IV-VIII have been investigated using the techniques of X-ray diffraction, optical and transmission electron microscopy. Phase and structural information is given on the non-equilibrium and metastable modifications occurring in these alloys after quenching from high-temperature β-field and aging. The conditions of the orthorhombic α″-phase, ω-phase and metastable β-phase formation in binary titanium–base alloys with d-metals of V-VIII groups were investigated. It was established that the position of the alloying metal in the Periodic Table defines the presence or absence of the α″-phase in the alloy after quenching and the minimum concentration of the alloying metal necessary for formation of the α″-phase, ω-phase and metastable β-phase.

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”.

HRTEM Observation of α-Phase in Cu-Zn Alloy Annealed at Lower Temperature

2007 ◽  
Vol 26-28 ◽  
pp. 1279-1282 ◽  
Author(s):  
Koji Kato ◽  
Daisuke Hamatani ◽  
Kenji Matsuda ◽  
Tokimasa Kawabata ◽  
Yasuhiro Uetani ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Phase ◽  
Phase Decomposition ◽  
Β Phase ◽  
Α Phase ◽  
Transmission Electron ◽  
Hrtem Observation ◽  
Lower Temperature ◽  
Zn Alloy

It is known that the phase-decomposition process of 60/40 Cu-Zn alloy is so-called the bainitic transformation, and decomposition of α-phase from the β’-phase is as follow: β’ → α9R → αfcc. In this work,decomposition of α-phase from the β’ single phase of Cu-40.26at.%Zn alloy has been investigated by high-resolution transmission electron microscopy (HRTEM) to understand the phase transformation of this alloy. Especially, striations in the α-phase has been focused on the special feature for the change of the structure and hardening of this alloy during annealing. The result of a comparison between this alloy and the Si added alloy is also reported.

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

scholarly journals High-pressure torsion-induced phase transformations and grain refinement in Al/Ti composites

2017 ◽  
Vol 52 (20) ◽  
pp. 12170-12184 ◽  
Author(s):  
Y. Sun ◽  
M. Aindow ◽  
R. J. Hebert ◽  
T. G. Langdon ◽  
E. J. Lavernia
Keyword(s):  
High Pressure ◽  
Phase Transformations ◽  
Grain Refinement ◽  
High Pressure Torsion

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

A Transmission Electron Microscopy Study of Decomposition in the Zn-Al Eutectoid Alloy

1975 ◽  
Vol 33 ◽  
pp. 26-27
Author(s):  
K. Nuttall
Keyword(s):  
Electron Microscopy ◽  
Superplastic Deformation ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Eutectoid Reaction ◽  
Transmission Electron Microscopy Study ◽  
Β Phase ◽  
Α Phase ◽  
Transmission Electron ◽  
Eutectoid Alloy

There has been considerable interest in the Zn-Al eutectoid alloy in recent years mainly because it exhibits superplastic deformation under certain conditions. A feature of particular importance is that the microstructural requirements for superplasticity can be achieved.in this alloy by heat treatment alone. However in spite of this, the mechanisms of phase transformation have not been widely studied; some aspects of these are described in this paper. The eutectoid reaction takes place at a composition of 78 wt% Zn and a temperature of 276°C by the decomposition of the high temperature γ phase (F.C.C.) to the Zn-rich β phase (C.P.H.) and the Al-rich α phase (F.C.C.) terminal solid solutions. Experiments have mainly involved quenching directly from the γ - phase field and isothermally transforming at various temperatures below 276°C.

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