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

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.

scholarly journals The Nucleation and the Intrinsic Microstructure Evolution of Martensite from 332113β Twin Boundary in β Titanium: First-Principles Calculations

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1202 ◽  
Author(s):  
Chen ◽  
Ma ◽  
Wang
Keyword(s):  
Twin Boundary ◽  
Microstructure Evolution ◽  
First Principles ◽  
Atomic Scale ◽  
Clear Understanding ◽  
Intermediate Structure ◽  
First Principles Calculations ◽  
Ti Alloys ◽  
Α Phase ◽  
Strength And Ductility

A clear understanding on the inter-evolution behaviors between 332113β twinning and stress-induced martensite (SIM) α″ in β-Ti alloys is vital for improving its strength and ductility concurrently. As the preliminary step to better understand these complex behaviors, the nucleation and the intrinsic microstructure evolution of martensite α″ from 332113β twin boundary (TB) were investigated in pure β-Ti at atomic scale using first-principles calculations in this work. We found the α″ precipitation prefers to nucleate and grow at 332113β TB, with the transformation of 332113β TB→130310α” TB. During this process, α″ precipitation firstly nucleates at 332113β TB and, subsequently, it grows inwards toward the grain interiors. This easy transition may stem from the strong crystallographic correspondence between 332113β and 130310α” TBs, and the region close to the 332113β TB presents the characteristics of intermediate structure between β and α″ phases. Kinetics calculations indicate the α″ phase barrierlessly nucleates at 332113β TB rather than in grain interior, where there is higher critical driving energy. Our calculations provide a unique perspective on the “intrinsic” microstructure evolution of martensite α″ from 332113β TB, which may deepen our understanding on the precipitation of martensite α″ and the inter-evolution behaviors between 332113β twinning and martensite α″ in β-Ti alloys at atomic scale.

Investment Casting of Ti Alloys for Biomedical Application

2006 ◽  
Vol 510-511 ◽  
pp. 794-797
Author(s):  
Si Young Sung ◽  
Young Jig Kim
Keyword(s):  
Formation Mechanism ◽  
Biomedical Application ◽  
Melting Furnace ◽  
Formation Mechanisms ◽  
Interstitial Oxygen ◽  
Reaction Products ◽  
Thermodynamic Consideration ◽  
Electron Probe Micro Analyzer ◽  
Ti Alloys ◽  
Net Shape Forming

The aim of this study is to clarify the alpha-case formation mechanisms for the economic net-shape forming of Ti and Ti alloys. The α-case formation reaction between Ti and Al2O3 mold was examined in a plasma arc melting furnace. The reaction products were characterized by using an electron probe micro-analyzer and transmission electron microscopy. The α-case generation between Ti and Al2O3 mold could not be explained by the conventional α-case formation mechanism, which is known to be formed by the interstitials, especially oxygen dissolved from mold materials. However, on the basis of our experimental results and thermodynamic consideration, it was confirmed that the α-case is formed not only by interstitial oxygen atoms but also by substitutional metal atoms dissolved from mold materials. Based on the α-case formation mechanism, α-case free net-shape forming of Ti and Ti alloys could be possible for biomedical applications.

Formation mechanism of α lamellae during β→α transformation in polycrystalline dual-phase Ti alloys

2021 ◽  
Vol 71 ◽  
pp. 98-108
Author(s):  
Jia Sun ◽  
Min Qi ◽  
Jinhu Zhang ◽  
Xuexiong Li ◽  
Hao Wang ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Dual Phase ◽  
Ti Alloys

scholarly journals Formation Mechanism of Nano-Strengthening Particles in Dispersion Strengthened W-Ti Alloys

2020 ◽  
Vol 15 (0) ◽  
pp. 1205021-1205021 ◽  
Author(s):  
Hiroyuki NOTO ◽  
Yoshimitsu HISHINUMA ◽  
Takeo MUROGA ◽  
Hideo BENOKI
Keyword(s):  
Formation Mechanism ◽  
Ti Alloys ◽  
Strengthening Particles

Phase Constitution and Mechanical Properties of Ti-(Cr, Mn)-Sn Biomedical Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 2118-2121 ◽  
Author(s):  
Yasuhiro Kusano ◽  
Tomonari Inamura ◽  
Hiroyasu Kanetaka ◽  
Shuichi Miyazaki ◽  
Hideki Hosoda
Keyword(s):  
Mechanical Properties ◽  
Binary Alloys ◽  
Xrd Analysis ◽  
Lattice Parameter ◽  
Medical Applications ◽  
Phase Constitution ◽  
Atom Ratio ◽  
Ti Alloys ◽  
Ω Phase ◽  
Mn Substitution

In order to produce new β (bcc) Ti alloys for medical applications, effects of Mn substitution for Cr on phase constitution and mechanical properties of Ti-Cr-Sn alloys were investigated. All the Ti-7mol%(Cr, Mn)-3mol%Sn alloys investigated by XRD analysis were identified as β (bcc) alloys, and athermal ω phase was also detected in Ti-7mol%Mn-3mol%Sn . The lattice parameter of β was slightly decreased by Mn substitution. Besides, the Mn substitution for Cr raised the hardness and the strength while reduced the ductility of the Ti-Cr-Sn alloys. The hardening by Mn substitution must be due to ω precipitation. The hardening is discussed from the viewpoint of electron atom ratio (e/a) in comparison with Ti-Cr binary alloys in the literature.

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