Formation of β-Ti Phase in Multi-component Gamma Alloys

2002 ◽  
Vol 753 ◽  
Author(s):  
Satoru Kobayashi ◽  
Masao Takeyama ◽  
Takahiro Motegi ◽  
Noriaki Hirota ◽  
Takashi Matsuo
Keyword(s):  
Ternary System ◽  
Critical Concentration ◽  
Phase Region ◽  
Group Element ◽  
Hot Workability ◽  
Quaternary Alloys ◽  
Two Phase ◽  
Β Phase ◽  
Bcc Phase ◽  
Quasi Ternary System

ABSTRACTEffect of combined addition of elements on the formation of high-temperature β-Ti (bcc) phase in Ti-45Al-M1-M2 quaternary alloys has been examined by converting the quaternary system to quasi-ternary system using M1-equivalency of M2: [M1] eq = k [M2]. The k value is evaluated from the ratio of critical concentration, XcM, to form the β phase in the isothermal section of each ternary system at 1473 K: kM1/M2= XcM1/XcM2. In case that M1 and M2 are in the same group element, Mo-equivalency of Cr, kMo/Cr = 0.46 and Nb-equivalency of V, kNb/V = 0.57. The critical concentrations to form the β phase in the quaternary systems become lower than those estimated from these values, and the experimentally determined equivalencies become 0.8 and 1.0, respectively. These results suggest an existence of negative interaction between M1 and M2 to stabilize the β phase even if they were in the same group element. Experimentally determined quaternary phase diagram revealed that the combined addition makes the β+α two-phase region expand to lower temperatures, thereby effective in improving hot workability for development of wrought gamma alloys.

Microstructural Evolution and Mechanical Properties of Al3-based Multi-Phase Alloys

2000 ◽  
Vol 646 ◽  
Author(s):  
Seiji Miura ◽  
Juri Fujinaka ◽  
Rikiya Nino ◽  
Tetsuo Mohri
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Ternary System ◽  
Phase Region ◽  
Quaternary Alloys ◽  
Two Phase ◽  
System A ◽  
Preliminary Study ◽  
Multi Phase ◽  
Bcc Phase

ABSTRACTA preliminary study on the phase relations in Al-Mo-Ti-X quaternary systems in the vicinity of Ti-trialuminide phases is carried out with various additives X= Mn, Cr, Fe, Ni and Ag. In the Al-Mo-Ti ternary system, a bcc-phase field extends from the Ti-Mo edge to high Al region at high temperatures and it equilibrates with a DO22-Al3Ti phase containing a large amount of Mo. It is found that, by additions of X= Mn, Cr, Fe or Ni, an L12-(Al, X)3 Ti phase appears near the two-phase region composed of the DO22-Al3 Ti and bcc phases in the Al-Mo-Ti ternary system. By heat treatment at 1223 K, the bcc phase of quaternary alloys decomposes into the A15-Mo3Al, DO22, L12 and/or σ phases, and no voids are observed. The mechanical properties of these alloys are also investigated by Vickers hardness.

scholarly journals The High-Temperature Deformation Behavior of As-Cast Ti90 Titanium Alloy

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1630
Author(s):  
Ke Wang ◽  
Yongqing Zhao ◽  
Weiju Jia ◽  
Silan Li ◽  
Chengliang Mao
Keyword(s):  
Titanium Alloy ◽  
Deformation Behavior ◽  
Processing Map ◽  
Electron Backscatter Diffraction ◽  
Phase Region ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Two Phase ◽  
Temperature Range ◽  
Β Phase

Isothermal compressions of as-cast near-α Ti90 titanium alloy were carried out on a Gleeble-3800 simulator in the temperature range of 860–1040 °C and strain rates of 0.001–10 s−1. The deformation behavior of the alloy was characterized based on the analyses of flow curves, the constructions of Arrhenius constitutive equations and the processing map. The microstructure evolution of the alloy was analyzed using the optical microscopic (OM), transmission electron microscope (TEM), and electron backscatter diffraction (EBSD) techniques. The results show that the kinking and dynamic globularization of α lamellae is the dominant mechanism of flow softening in the α + β two-phase region, while the dynamic recovery (DRV) of β phase is the main softening mechanism in the β single-phase region. The dynamic globularization of α lamellae is mainly caused by the wedging of β phase into α laths and the shearing of α laths due to imposed shear strain. The activation of prismatic and pyramidal slip is found to be easier than that of basic slip during the deformation in the α + β two-phase region. In addition, the Schmid factor of equiaxial α is different from that of lamellar α, which also varies with the angle between its geometric orientation and compression direction (CD). Based on the processing map, the low η region within the temperature range of 860–918 °C with a strain rate range of 0.318–10 s−1 should be avoided to prevent the occurrence of deformation instability.

Effect of hot-forging on beta phase transformation of a high niobium containing titanium aluminide alloy

2015 ◽  
Vol 29 (10n11) ◽  
pp. 1540009
Author(s):  
Liang Cheng ◽  
Xiangyi Xue ◽  
Bin Tang ◽  
Hongchao Kou ◽  
Jinshan Li
Keyword(s):  
Titanium Aluminide ◽  
Volume Fraction ◽  
Hot Forging ◽  
Beta Phase ◽  
Phase Region ◽  
Practical Significance ◽  
Hot Workability ◽  
Present Alloy ◽  
Β Phase ◽  
B2 Phase

In this paper, ingot breakdown process of a high Nb containing TiAl alloy with a chemical composition of Ti –42.63 Al –8.11 Nb –0.21 W –0.09 Y (at.%) has been investigated under conventional forging conditions. It was found that the present alloy possesses superior hot-workability that can be successfully forged by conventional upsetting route due to the appearance of large amount of β/B2 phase, though shear band was observed in the forged-pancake. Further studies revealed that hot-working performed in (α + β) phase region which can effectively impede the β → α transformation and thus significantly increase the volume fraction of β/B2 phase. In contrast, the amount of β/B2 phase was notably reduced by heat treatment at the same conditions. This stress-induced effect is considered to be responsible to the superior hot-workability of the present alloy and the mechanism has been discussed and reasonably clarified. It was also suggested that the stress-induced effect has practical significance that it allows the implementation of conventional multi-step forging process which can develop fine and uniform microstructures suitable for secondary processing.

Phase Equilibria and Lattice Parameters of Fe2Nb Laves Phase in Fe-Ni-Nb Ternary System at Elevated Temperatures

2004 ◽  
Vol 842 ◽  
Author(s):  
Masao Takeyama ◽  
Nobuyuki Gomi ◽  
Sumio Morita ◽  
Takashi Matsuo
Keyword(s):  
Ternary System ◽  
Phase Equilibria ◽  
Elevated Temperatures ◽  
Phase Region ◽  
Lattice Parameters ◽  
Laves Phase ◽  
Austenitic Steels ◽  
Dominant Factor ◽  
Two Phase ◽  
Ni Content

ABSTRACTPhase equilibria in Fe-Ni-Nb ternary system at elevated temperatures have been examined, in order to identify the two-phase region of γ-Fe (austenite) and ε-Fe2Nb (C14). The ε single phase region exists in the range of 27.5 to 35.5 at.% Nb in the Fe-Nb binary system, and it extends toward the equi-niobium concentration direction up to 44 at.% Ni in the ternary system at 1473 K, indicating that more than half of the Fe atoms in Fe2Nb can be replaced with Ni. Thus, the γ+ε two-phase region exists extensively, and the solubility of Nb in γ phase increases from 1.5 to 6.0 at.% with increase in Ni content. The lattice parameters of a and c in the C14 Laves phase decrease with increasing Ni content. The change in a axis is in good agreement with calculation based on Vegard's law, whereas that of c axis is much larger than the calculated value. The result suggests that atomic size effect is responsible for a-axis change and the binding energy is dominant factor for the c-axis change. To extend these findings to development of new class of austenitic steels strengthened by Laves phase, an attempt has been made to control the c/a ratio by alloying. The addition of Cr is effective to make the c/a ratio close to the cubic symmetry value (1.633).

Phase Stability of Sigma + Beta Microstructures in the Ternary Nb-Ti-Al System

1990 ◽  
Vol 194 ◽  
Author(s):  
D. T. Hoelzer ◽  
F. Ebrahimi
Keyword(s):  
Phase Stability ◽  
Orthorhombic Phase ◽  
Beta Phase ◽  
Phase Region ◽  
Nominal Composition ◽  
Two Phase ◽  
Σ Phase ◽  
Β Phase ◽  
Heat Treated ◽  
The Stability

AbstractAn alloy with the nominal composition 42Nb-28Ti-30Al (at.%) was heat treated in the sigma + beta phase region. The evolution of σ phase from the metastable β phase and the stability of the two-phase microstructure at various aging temperatures were evaluated using TEM techniques. The results indicate that the β phase in equilibrium with the σ phase at high temperatures decomposes to the orthorhombic phase at temperatures below 1200°C.

Phase Equilibria among γ-Fe, γ-Fe and Fe2Mo Phases and Stability of the Laves Phase in Fe-Mo-Ni Ternary System at Elevated Temperatures

2006 ◽  
Vol 980 ◽  
Author(s):  
Shigehiro Ishikawa ◽  
Takashi Matsuo ◽  
Masao Takeyama
Keyword(s):  
Ternary System ◽  
Phase Equilibria ◽  
Elevated Temperatures ◽  
Phase Region ◽  
Homogeneity Region ◽  
Nickel Concentration ◽  
Peritectoid Reaction ◽  
Two Phase ◽  
Three Phase ◽  
Binary Edge

AbstractPhase equilibria among the bcc Fe(α), fcc Fe(γ) and Fe2Mo(λ)_phases in Fe-Mo-Ni ternary system, particularly paying attention to the existence of the γ+λ two-phase region, have been examined at elevated temperatures below Tc (1200 K), the peritectoid reaction temperature in Fe-Mo binary system: λ?α+Fe7Mo6 (μ). At 1173 K the α+γ+μ three-phase coexisting region exists near the Fe-Mo binary edge and no λ phase region was identified. At 1073 K the λ phase in equilibrium with α and γ phases exists, although the composition homogeneity region of the ternary λ phase was limited to its binary edge toward the equi-nickel concentration direction up to about 3at % Ni. Instead, large two-phase region of γ+μ was extended along the same direction up to 20 at% Ni. The γ+λ two-phase region appears below Tc through a transition peritectoid reaction: α+μ¨γ+λ. The γ phase in equilibrium with λ phase is stable only at elevated temperatures, and it transforms martensitically to α phase during cooling. The addition of Ni stabilizes γ and μ phases against α and λ phases, thereby decreasing the relative stability of the λ phase.

Phase Equilibria between γ-Fe (A1) and Fe2Ti Laves (C14) Phases and Microstructure in Fe-Ti-Ni Ternary System at Elevated Temperatures

2007 ◽  
Vol 561-565 ◽  
pp. 435-438 ◽  
Author(s):  
Tomoaki Sugiura ◽  
Shigehiro Ishikawa ◽  
Takashi Matsuo ◽  
Masao Takeyama
Keyword(s):  
Ternary System ◽  
Phase Equilibria ◽  
Elevated Temperatures ◽  
Eutectic Reaction ◽  
Ternary Eutectic ◽  
Phase Region ◽  
Two Phase ◽  
Ni Addition ◽  
Element Addition ◽  
Rich Side

The phase equilibria among α-Fe, γ-Fe and Fe2Ti phases in Fe-Ti-Ni ternary system at 1473 K and 1373 K with Ni (γ former element) addition were examined, by paying attention to the γ+Fe2Ti two-phase region. The Fe2Ti single-phase region extends toward the equal-titanium concentration direction up to about 30 at% Ni, and the Laves phase becomes in equilibrium with γ-Fe by 12 at% Ni addition, but the γ+Fe2Ti two-phase region is limited because of the formation of liquid phase by further Ni addition at 1473 K. With decreasing temperature, a ternary eutectic reaction (L→γ-Fe+Fe2Ti+Ni3Ti) occurs, making the two-phase region wider just below the invariant reaction at 1373 K, and the region becomes narrower again by the enlargement of the three-phases region toward Fe-rich side.

scholarly journals Post-dynamic α to β phase transformation and reverse transformation of Ti-5Al-3V alloy after hot deformation in two phase region

2020 ◽  
Vol 188 ◽  
pp. 108466 ◽  
Author(s):  
Xiankun Ji ◽  
Hong Yu ◽  
Baoqi Guo ◽  
Fulin Jiang ◽  
Dingfa Fu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Hot Deformation ◽  
Phase Region ◽  
Reverse Transformation ◽  
Two Phase ◽  
Β Phase

Hot Deformation Behavior of Near-α Ti-Fe Alloy in (α+β) Two-Phase Region with Different Fe Content

2010 ◽  
Vol 638-642 ◽  
pp. 310-314
Author(s):  
Behrang Poorganji ◽  
Makoto Yamaguchi ◽  
Yoshio Itsumi ◽  
Katsushi Matsumoto ◽  
Tomofumi Tanaka ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Deformation Temperature ◽  
Interlamellar Spacing ◽  
Phase Region ◽  
Strain Rates ◽  
Two Phase ◽  
Β Phase ◽  
Α Phase ◽  
Fe Content

In the present study, microstructure evolution of Ti-Fe alloys with different Fe content between 0.2-1.5mass% during hot deformation in (α+β) two-phase region is studied with focusing on effect of phase volume fraction at different deformation temperatures and strain rates. Hot deformation was conducted on the specimens quenched after β solutionizing at 1173K for 1.2ks at 1108, 1073 and 948K, by uniaxial compression by 50% at various strain rates ranged from 1 to 10-4 s-1. Initial structures are (α+β) lamellar structures of fine interlamellar spacing and colony sizes. Increase in Fe content results in increasing the fraction of the β phase at the given deformation temperature. Either colony size or interlamellar spacing is coarser at higher temperatures. At the higher deformation temperature where β phase fraction is larger, dynamic recovery of β phase is a major deformation mechanism while at a lower temperature, i.e., a higher α fraction, dynamic recrystallization of α phase occurs predominantly. It is concluded that critical strain needed for occurrence of dynamic recrystallization is decreased by increasing fraction of the α phase at the same deformation temperature, i.e., by decreasing Fe content. Furthermore, by increasing strain rate grain size of the recrystallized α is decreased.

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