Modelling the β → ω Phase Transformations in Ti- Alloys Through a 4D Structural Description

2020 ◽  
Author(s):  
Soham Mukherjee ◽  
Rajiv Kumar Mandal
Keyword(s):  
Phase Transformations ◽  
Structural Description ◽  
Ti Alloys ◽  
Ω Phase

scholarly journals First principles computation of composition dependent elastic constants of omega in titanium alloys: implications on mechanical behavior

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Salloom ◽  
S. A. Mantri ◽  
R. Banerjee ◽  
S. G. Srinivasan
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
First Principles ◽  
Young's Modulus ◽  
Group Vi ◽  
Group V ◽  
Β Phase ◽  
Ti Alloys ◽  
Ω Phase ◽  
Stabilizer Concentration

AbstractFor decades the poor mechanical properties of Ti alloys were attributed to the intrinsic brittleness of the hexagonal ω-phase that has fewer than 5-independent slip systems. We contradict this conventional wisdom by coupling first-principles and cluster expansion calculations with experiments. We show that the elastic properties of the ω-phase can be systematically varied as a function of its composition to enhance both the ductility and strength of the Ti-alloy. Studies with five prototypical β-stabilizer solutes (Nb, Ta, V, Mo, and W) show that increasing β-stabilizer concentration destabilizes the ω-phase, in agreement with experiments. The Young’s modulus of ω-phase also decreased at larger concentration of β-stabilizers. Within the region of ω-phase stability, addition of Nb, Ta, and V (Group-V elements) decreased Young’s modulus more steeply compared to Mo and W (Group-VI elements) additions. The higher values of Young’s modulus of Ti–W and Ti–Mo binaries is related to the stronger stabilization of ω-phase due to the higher number of valence electrons. Density of states (DOS) calculations also revealed a stronger covalent bonding in the ω-phase compared to a metallic bonding in β-phase, and indicate that alloying is a promising route to enhance the ω-phase’s ductility. Overall, the mechanical properties of ω-phase predicted by our calculations agree well with the available experiments. Importantly, our study reveals that ω precipitates are not intrinsically embrittling and detrimental, and that we can create Ti-alloys with both good ductility and strength by tailoring ω precipitates' composition instead of completely eliminating them.

Effects of Cooling Rate and Sn Addition on the Microstructure of Ti-Nb-Sn Alloys

2011 ◽  
Vol 172-174 ◽  
pp. 190-195 ◽  
Author(s):  
Giorgia T. Aleixo ◽  
Eder S.N. Lopes ◽  
Rodrigo Contieri ◽  
Alessandra Cremasco ◽  
Conrado Ramos Moreira Afonso ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Melting Furnace ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
Arc Melting ◽  
Ti Alloys ◽  
Ω Phase

Ti-based alloys present unique properties and hence, are employed in several industrial segments. Among Ti alloys, β type alloys form one of the most versatile classes of materials in relation to processing, microstructure and mechanical properties. It is well known that heat treatment of Ti alloys plays an important role in determining their microstructure and mechanical behavior. The aim of this work is to analyze microstructure and phases formed during cooling of β Ti-Nb-Sn alloy through different cooling rates. Initially, samples of Ti-Nb-Sn system were prepared through arc melting furnace. After, they were subjected to continuous cooling experiments to evaluate conditions for obtaining metastable phases. Microstructure analysis, differential scanning calorimetry and X-ray diffraction were performed in order to evaluate phase transformations. Depending on the cooling rate and composition, α” martensite, ω phase and β phase were obtained. Elastic modulus has been found to decrease as the amount of Sn was increased.

New insights into formation mechanism of interfacial twin boundary ω-phase in metastable β-Ti alloys

2020 ◽  
Vol 164 ◽  
pp. 110363 ◽  
Author(s):  
Wei Chen ◽  
Shuo Cao ◽  
Jinyu Zhang ◽  
You Zha ◽  
Qingmiao Hu ◽  
...  
Keyword(s):  
Twin Boundary ◽  
Formation Mechanism ◽  
Ti Alloys ◽  
Ω Phase

Phase Transformations in Nb-Al-Ti alloys

1996 ◽  
Vol 27 (6) ◽  
pp. 1647-1659 ◽  
Author(s):  
E. S. K. Menon ◽  
P. R. Subramanian ◽  
D. M. Dimiduk
Keyword(s):  
Phase Transformations ◽  
Ti Alloys

Phase transformations in Fe3AL + Ti alloys

1994 ◽  
Vol 55 (6) ◽  
pp. 505-515 ◽  
Author(s):  
C.H. Sellers ◽  
T.A. Hyde ◽  
T.K. O'Brien ◽  
R.N. Wright
Keyword(s):  
Phase Transformations ◽  
Ti Alloys

Phase transformations in dilute U-TI alloys

1986 ◽  
Vol 121 ◽  
pp. 483-486 ◽  
Author(s):  
G. Kimmel ◽  
A. Landau ◽  
J. Sariel ◽  
U. Admon
Keyword(s):  
Phase Transformations ◽  
Ti Alloys

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 Transformations in Beta-Ti Alloys Studied by In-Situ Methods

2016 ◽  
pp. 437-441 ◽  
Author(s):  
Petr Harcuba ◽  
Jana Šmilauerová ◽  
Máhal Hájek ◽  
Pavel Zháňal ◽  
Jan Čapek
Keyword(s):  
Phase Transformations ◽  
Ti Alloys ◽  
In Situ Methods

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.

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