TWO EQUATIONS OF STATE CONSIDERING THE THERMAL EFFECT FOR α, β AND ω PHASES OF ZIRCONIUM

2008 ◽  
Vol 22 (03) ◽  
pp. 167-180
Author(s):  
RONGGANG TIAN ◽  
JIUXUN SUN ◽  
CHAO ZHANG ◽  
FULONG WANG
Keyword(s):  
Experimental Data ◽  
Thermal Effect ◽  
Equations Of State ◽  
Zero Point ◽  
Hexagonal Structure ◽  
Zero Temperature ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Einstein Model

The Baonza and mGLJ equations of state (EOS) modified previously to consider the thermal effect are applied to study the thermodynamic properties of Zirconium (Zr) . It is proposed that the zero-point vibration term should be deleted in a thermal EOS, and the parameters cannot be directly taken as experimental data at a reference temperature, [Formula: see text] and [Formula: see text], but their values at absolute zero temperature, [Formula: see text] and [Formula: see text]. Based on the Einstein model, an approach is proposed to solve [Formula: see text] and [Formula: see text] from [Formula: see text] and [Formula: see text]. For the hcp (α phase), bcc (β phase) and hexagonal structure (ω phase) of Zr , the molar volume (V), isothermal bulk modulus (B) and thermal expansion coefficient (α) was calculated as a function of pressure and temperature. The predictive capabilities of the complete EOS are discussed and compared with experimental data.

Phase Constitution and Heat Treatment Behavior of Zr-Nb Alloys

2007 ◽  
Vol 561-565 ◽  
pp. 1435-1440 ◽  
Author(s):  
Masahiko Ikeda ◽  
Tsuyoshi Miyazaki ◽  
Satoshi Doi ◽  
Michiharu Ogawa
Keyword(s):  
Heat Treatment ◽  
Elastic Modulus ◽  
Elastic Moduli ◽  
X Ray Diffraction ◽  
Phase Constitution ◽  
X Ray ◽  
Β Phase ◽  
Ω Phase ◽  
Solution Treated ◽  
Α Phase

Phase constitution in the solution-treated and quenched state and the heat treatment behavior were investigated by electrical resistivity, hardness, and elastic modulus measurements, X-ray diffraction, and optical microscopy. Hexagonal martensite and the β phase were identified in the Zr-5mass%Nb alloy. β and ω phases were identified in the Zr-10 and 15mass%Nb alloys, and only the β phase was identified in the Ti-20Nb alloy. Resistivity at RT, Vickers hardness and elastic modulus increased up to 10Nb and then decreased dramatically at 15Nb. Above 15Nb, these values slightly decreased. The elastic moduli for 15Nb and 20Nb were 59.5 and 55.5 GPa, respectively. On isochronal heat treatment, the isothermal ω phase precipitated between 473 and 623 K and then the α phase precipitated in the 10Nb, 15Nb and 20Nb alloys.

scholarly journals Phase transformations during continuous heating: effect of Sn addition on the microstructure of Ti-13Mo alloy

2020 ◽  
Vol 321 ◽  
pp. 05017
Author(s):  
M.G. de Mello ◽  
F.H. da Costa ◽  
R. Caram
Keyword(s):  
Lattice Parameter ◽  
Continuous Heating ◽  
Phase Precipitation ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Heat Treated ◽  
Kinetics Of

The addition of Sn to the Ti-Mo system can diminish the formation of ω phase and slow down the precipitation kinetics of α phase due to the low atomic diffusivity of Sn atoms in Ti. To explore α phase precipitation in Ti-13Mo and Ti-13Mo-6Sn (wt.%) alloys, differential scanning calorimetry (DSC) was applied using different heating rates to determine ω phase dissolution, α phase precipitation and β transus temperatures. The DSC results were then used to determine the aging heat treatment temperatures. Samples were heat-treated at 600 °C for 1 h and 24 h to examine microstructure features. The addition of Sn to Ti-13Mo alloy was found to increase the β phase lattice parameter, increasing β transus temperatures and resulting in microstructures with heterogeneous and coarser α phase precipitation.

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.

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.

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.

Precipitation of β' Phase in a Low Cost Beta Titanium Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 461-464 ◽  
Author(s):  
Tatsuaki Sakamoto ◽  
Yuri Hiagaki ◽  
Sengo Kobayashi ◽  
Kiyomichi Nakai
Keyword(s):  
Low Cost ◽  
Solution Treatment ◽  
Lattice Parameter ◽  
Nucleation Site ◽  
Precipitation Behavior ◽  
Beta Titanium Alloy ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Beta Titanium

Precipitation behavior of a metastable β Ti alloy, Ti-6.8Mo-4.5Fe-1.5Al(masss%), during two-step aging has been investigated. Supersaturated β phase after solution treatment decomposes into β+ω phases during the first aging at 300°C for 2ks. β′ phase is observed during the second aging at 500°C for 50s. It is suggested that reverse transformation of the ω phase to β phase during the second aging at 500°C for 50s gives rise to solute-lean and –rich regions in the β phase, and that β′ phase is formed in the solute-rich region. β′ phase being coherent with β phase has larger lattice parameter than β phase. β′ phase acts as nucleation site for α phase, and accelerates the nucleation of α phase.

Effect of Oxygen Content on Microstructure and Mechanical Properties of Ti-Nb-Ge Alloys for Biomedical Application

2008 ◽  
Vol 47-50 ◽  
pp. 1450-1453 ◽  
Author(s):  
Won Yong Kim ◽  
Han Sol Kim
Keyword(s):  
Mechanical Properties ◽  
Oxygen Content ◽  
Volume Fraction ◽  
Biomedical Application ◽  
Casting Process ◽  
Alloy System ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
The Stability

The effect of Ge and oxygen content on microstructural formation and mechanical properties of Ti-Nb alloys were investigated in order to design a desirable Ti based alloy through casting process. Three phase mixtures consisting of bcc-structured β phase, orthorhombic structured α" phase and intermediate ω phase were found depending on Nb, Ge, oxygen content in the present alloy system. The volume fraction of α" phase and ω phase decreased with increasing Ge or oxygen content. This microstructural information may indicate that both Ge and oxygen act to increase the stability of β phase rather than α" phase in metastable β-Ti based alloys prepared by water quenching. Elastic modulus values were sensitive to phase stability of constituent phases.

scholarly journals Affect of prolonged thermal exposure on microstructure and mechanical properties of ultrafine-grained bioinert Zr - 1 wt. % Nb and Ti - 45 wt. % Nb alloys

2020 ◽  
pp. 9-16
Author(s):  
A.Yu. Eroshenko ◽  
◽  
Yu.P. Sharkeev ◽  
M.A. Khimich ◽  
P.V. Uvarkin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Exposure ◽  
Annealing Duration ◽  
Structural Elements ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Microstructure And Mechanical Properties ◽  
Ultrafine Grained ◽  
The Matrix

The results for thermal stability of the microstructure and mechanical properties of ultrafine-grained alloys Zr-1 wt. % Nb and Ti-45 wt. % Nb alloys after long-term thermal annealing at temperature of 400°C are presented. It is shown that in the Zr-1 wt.%Nb alloy in the ultrafine-grained state, increase in the annealing duration from 5 to 360 hours leads to growth of the structural elements (grains, sub-grains, fragments) of the matrix phase a - Zr and the particles β-Nb. This fact is due to the processes of recrystallization. It leads to softening of the alloy and decrease of microhardness and yield stress. It was also found that annealing up to 360 hours does not affect the size of the structural elements of the matrix β-phase in the Ti-45 wt. % Nb alloy, but contributes to the noticeable growth of the α-phase and ω-phase grains. According to our results, softening of the Ti-45 wt. % Nb alloy and decrease in its mechanical characteristics are associated with the processes of return at the grain boundaries, as well as with growth of the nanoscale grains of α-phase and ω-phase and decrease in their contribution to dispersion hardening.

scholarly journals CoSO4·H2O and its continuous transition compared to the compression properties of isostructural kieserite-type polymorphs

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Manfred Wildner ◽  
Martin Ende ◽  
Johannes M. Meusburger ◽  
Roland Kunit ◽  
Philipp Matzinger ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Space ◽  
Equations Of State ◽  
Driving Mechanism ◽  
Volume Data ◽  
Continuous Transition ◽  
Space Group ◽  
Β Phase ◽  
Bonding System ◽  
Α Phase

Abstract The kieserite-type compound cobalt(II) sulfate monohydrate, CoSO4·H2O, has been investigated under isothermal (T = 295 K) hydrostatic compression up to 10.1 GPa in a diamond anvil cell by means of single-crystal X-ray diffraction and Raman spectroscopy. The monoclinic α-phase (space group C2/c) undergoes a second-order ferroelastic phase transition at P c  = 2.40(3) GPa to a triclinic β-phase (space group P 1 ‾ $‾{1}$ ). Lattice elasticities derived from fitting third-order Birch-Murnaghan equations of state to the pressure dependent unit-cell volume data yield V 0 = 354.20(6) Å3, K 0 = 53.0(1.7) GPa, K′ = 5.7(1.8) for the α-phase and V 0 = 355.9(8) Å3, K 0 = 45.2(2.6) GPa, K′ = 6.6(6) for the β-phase. Crystal structure data of the high-pressure polymorph were determined at 2.98(6) and 4.88(6) GPa. The most obvious structural feature and thus a possible driving mechanism of the phase transition, is a partial rearrangement in the hydrogen bonding system. However, a comparative analysis of pressure-induced changes in the four kieserite-type compounds investigated to date suggests that the loss of the point symmetry 2 at the otherwise rather rigid SO4 tetrahedron, allowing symmetrically unrestricted tetrahedral rotations and edge tiltings in the β-phase, could be the actual driving mechanism of the phase transition.

Thermal Stability and Mechanical Properties of Ti-15-3 Titanium Alloy

2016 ◽  
Vol 849 ◽  
pp. 232-237 ◽  
Author(s):  
Qing Rui Wang ◽  
Xing Wu Li ◽  
Ai Xue Sha ◽  
Xin Qing Zhao ◽  
Yong Qi Zhu
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Tensile Strength ◽  
Titanium Alloy ◽  
Aging Time ◽  
Β Phase ◽  
Ω Phase ◽  
Microstructure Stability ◽  
Α Phase ◽  
Strength And Ductility

The microstructure stability and tensile properties of Ti-15-3 titanium alloy were investigated by aging the alloy at different conditions. The results showed that when the temperature was below 250°C, ω phase precipitates and the tensile strength increased with increasing aging time. Although there were a little of ω phase after aging at 200C for 1000h, Ti-15-3 alloy still presented good strength and ductility. When the aging temperature was 250°C~400°C, ω precipitation or β’ phase separation occurred from β matrix, and finally transformed to α precipitates. The tensile strength increased firstly and then decreased with increasing aging time. When aged at above 400°C, α phase precipitated fast from the alloy, and the strength increased gradually.

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