From β-Phase Particle to α-Phase Hexagonal-Platelet Superstructure over AgGaO2: Phase Transformation, Formation Mechanism of Morphology, and Photocatalytic Properties

The phase transformations of the alloy Ti-40 mas % Nb after tempering and severe plastic deformation are studied. The phase transformations of the alloy according to the type and conditions of external influences are analyzed using methods of XRD, SEM and optical metallography. It is determined that inverse phase transformation of the metastable α''-phase to equilibrium β-phase is carried out after severe plastic deformation. Complete phase transformation α'' → β is typical for the mode, which consists of three pressing operation with the change of the loading axis in cramped conditions, followed by a multi-pass rolling in grooved rolls.

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Phase Transformation Cycle β→ α′ + α + α"→ β in Ti6Al4V Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.828-829.232 ◽

2015 ◽

Vol 828-829 ◽

pp. 232-238 ◽

Cited By ~ 2

Author(s):

Kalenda Mutombo ◽

Siyasiya Charles ◽

Waldo Stumpf

Keyword(s):

Thermal Expansion ◽

Phase Transformation ◽

Phase Field ◽

Xrd Analysis ◽

External Stress ◽

Ti6al4v Alloy ◽

Β Phase ◽

Α Phase ◽

Sequential Transformation ◽

Dsc Thermograms

The β-phase transforms to α′, α and α" within a range of temperature from the β-transus (Tβ) to about 600°C, considering no external stress is applied. Two types of microstructure were obtained: acicular martensite when rapidly cooled and lamellar α/β when slowly cooled from the β phase field. The sequential transformation of β into α′, α-phase, α2, and α" was revealed as peaks on the coefficient thermal expansion (CTE) curves, however, reversed transformations: α"→β, and α→β, were revealed by the DSC thermograms. The presence of β, α′, α, α2 and α" was identified by means of XRD analysis and HRTEM.

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X-ray study of the twinning and phase transformation of phosphocristobalite (AlPO4)

Canadian Journal of Physics ◽

10.1139/p77-095 ◽

1977 ◽

Vol 55 (7-8) ◽

pp. 677-683 ◽

Cited By ~ 13

Author(s):

H. N. Ng ◽

C. Calvo

Keyword(s):

Phase Transformation ◽

Transition Temperature ◽

Short Range ◽

X Ray ◽

First Order ◽

Β Phase ◽

Α Phase ◽

Short Range Correlations

Crystals of the cristobalite polymorph of AlPO4 (phosphocristobalite) up to 3 mm in breadth were grown from a V2O5 flux. In the α phase (C2221), the presence of twin domains prevents an accurate resolution of the structure as a function of temperature. The six twin components of this phase readily lead to a disordered β phase [Formula: see text] with short range correlations as suggested previously. The α–β transformation is first order with a substantial hysteresis in the transition temperature.

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Effect of Quenching and Reheating on Isothermal Phase Transformation in Ti-15Nb-10Zr Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.582 ◽

2010 ◽

Vol 638-642 ◽

pp. 582-587 ◽

Cited By ~ 2

Author(s):

Sengo Kobayashi ◽

Ryoichi Ohshima ◽

Kiyomichi Nakai ◽

Tatsuaki Sakamoto

Keyword(s):

Phase Transformation ◽

Solution Treatment ◽

The Other ◽

Matrix Microstructure ◽

Iced Brine ◽

Β Phase ◽

Solution Treated ◽

Α Phase ◽

Other Hand ◽

Means Of Transmission

Isothermal phase transformation in Ti-15Nb-10Zr (at%) alloys has been examined by mainly means of transmission electron microscopy. Specimens solution-treated at 1000°C in  phase field were directly held at temperatures between 350 and 450°C for 1.8-86.4ks, which are called "DH (direct holding)-specimen". On the other hand, some specimens solution-treated at 1000°C were quenched into iced brine and then aged at temperatures between 350 and 450°C, which are called "QA(quench and aging)-specimen". In the DH-specimen held at 400°C α phase formed in β matrix. Microstructure evolution of QA-specimen aged at 400°C, on the other hand, is as follows.  phase formed in β matrix after aging for 1.8ks and further aging led to growth of  phase. After prolonged aging, α phase started to form in β matrix. These experimental results indicate that process of the quenching and reheating promotes the formation of  phase. Specimen quenched into iced brine after solution treatment exhibited α'' phase formation. The α'' phase in the quenched specimen would transform into β phase during reheating to the aging temperature. Reversion process of α''  β phase could promote the formation of  phase in β. Microstructure formation in the DH- and QA-specimens at 350 and 450°C will also be explained.

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Investigation of phase transformation in Fe microalloyed Ti6Al4V alloy during continuous heating process

MATEC Web of Conferences ◽

10.1051/matecconf/202032112010 ◽

2020 ◽

Vol 321 ◽

pp. 12010

Author(s):

Changliang Wang ◽

Feng Li ◽

Can Ding ◽

Hui Chang ◽

Lian Zhou

Keyword(s):

Phase Transition ◽

Phase Transformation ◽

Expansion Method ◽

Ti6al4v Alloy ◽

Continuous Heating ◽

Heating Process ◽

Β Phase ◽

Α Phase ◽

Phase Transition Temperatures ◽

Evolution Of Microstructure

The phase transformation and dilatometric curves in Fe microalloyed Ti6Al4V alloy (Ti6Al4V-Fe) during continuous heating at 1 ℃ /min heating rate had been studied by dilatometer and metallographic methods, and β phase transition temperatures of alloy were obtained. In order to validate the accuracy of these β phase transition temperature and microstructure evolution, the relative phase concentration and the evolution of microstructure which were acquired by cooling after tempering were analyzed by metallographic microscope. The results illuminated that the expansion method was able to accurately measure the β transformation temperature of Ti6Al4V-Fe alloy. The lathy-shaped α phase decreased significantly disappeared in the range of 838℃ to 988℃, and the α→β phase transformation occurred.

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Thermal cycling induced δ to α phase transformation via an intermediate β phase on a δ-stabilized Pu–Ga alloy

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2012.03.056 ◽

2012 ◽

Vol 529 ◽

pp. 173-180 ◽

Cited By ~ 4

Author(s):

Michael Ling ◽

Andrew Perry

Keyword(s):

Phase Transformation ◽

Thermal Cycling ◽

Β Phase ◽

Α Phase

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Microstructural Evolution and Element Partitioning in the Phase Transformation of Ti-17 Alloy under Continuous Heating and Cooling Conditions

Metals ◽

10.3390/met10081054 ◽

2020 ◽

Vol 10 (8) ◽

pp. 1054

Author(s):

Xudong An ◽

Xin Cai ◽

Mingpan Wan ◽

Min Lei ◽

Chaowen Huang ◽

...

Keyword(s):

Electron Microscopy ◽

Phase Transformation ◽

Continuous Heating ◽

Alloying Element ◽

Heating And Cooling ◽

Β Phase ◽

Cooling Conditions ◽

Α Phase ◽

Element Partitioning ◽

The Matrix

The microstructural evolution and alloying element partitioning in the α + β ↔ β phase transformation of Ti-17 alloy were explored under continuous heating and cooling conditions using the dilatometric method. Scanning electron microscopy and transmission electron microscopy were used to evaluate microstructural characteristics and trace alloying element partitioning behaviors occurring at different temperatures during heating and cooling. Results showed that the finer needle-like α phase first dissolved into the β phase in the matrix with increasing temperature, while the grain boundary α phase first coarsened and then transformed gradually into β phase during continuous heating. The dissolution of α phase of the alloy with the alloying element partitioning during continuous heating was observed. On the contrary, αGB formed at the prior β grain of the alloy during continuous cooling, which might be the nuclei of α colony, thus resulting in the formation of α colony in the matrix. As the temperature decreased, the elements’ concentrations in the α and β phases became increasingly varied due to element partition. Moreover, Al and Cr, which had higher diffusion coefficients than Mo, easily reached the concentration equilibrium of alloying elements in the α and β phases, respectively. The shrinkage of dilatometric curves during heating in the Ti-17 alloy are mainly attributed to the change of α-HCP (hexagonal close-packed) lattice to β-BCC (body-centered cubic) lattice; while the element partitioning during the β → α + β transformation plays an important role in the shrinkage of the dilatometric curves of the Ti-17 alloy during cooling.

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Phase Transformation and Microstructure Evolution in Near-β Ti-7333 Titanium Alloy during Aging

Materials Science Forum ◽

10.4028/www.scientific.net/msf.747-748.904 ◽

2013 ◽

Vol 747-748 ◽

pp. 904-911 ◽

Cited By ~ 1

Author(s):

Qiong Hui ◽

Xiang Yi Xue ◽

Hong Chao Kou ◽

Min Jie Lai ◽

Bin Tang ◽

...

Keyword(s):

Titanium Alloy ◽

Phase Transformation ◽

Grain Boundaries ◽

Parent Phase ◽

Solution Treatment ◽

Ageing Treatment ◽

Β Phase ◽

Α Phase ◽

Nucleation Sites ◽

Higher Temperature

A newly near-β titanium alloy Ti-7Mo-3Cr-3Nb-3Al (Ti-7333) was subjected to β phase solution treatment and ageing in the present work. The characteristics of α phase transformation in ageing treatment were studied. Results show that isothermal aging at a low temperature (350) will result in lots of ω particles with small size homogeneously distributing in the parent phase. These ω particles can act as nucleation sites for α phase and lead to the uniform precipitation of fine α phase within the β grain after further ageing treatment. However, when ageing at a higher temperature, the α phase tends to precipitate direct from the β matrix and the morphology of α phase is determined by the temperature and period of ageing treatment. After aging at 550 for 5min, acicular α phase precipitates in the β grains as well as along β grain boundaries and the size and quantity of α phase increase with the holding time. Note that Ti-7333 alloy has a quick ageing response. When aging at 700 for 1h, coarser α laths precipitate both on the grain boundary and within the grain. Increase the ageing temperature to 800, α phase precipitates within the β grain as short rod-like morphology. It is suggested that the driving force for α phase nucleation and the amount of defects in the intragranular decrease with the increasing of temperature, leading to the grain boundaries become the prior nucleation sites. Substantial α phase precipitate-free regions adjacent to β grain boundaries remained after ageing at 700 for 1h due to the rejection of β-stabilizer from coarse α lath on β grain boundaries. Aging at 800 for 1h resulted in pronounced continuous α-films along β grain boundaries.

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

Microscopy and Microanalysis ◽

10.1017/s1431927621012277 ◽

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.

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Densification and α/β Phase Transformation of SHS Si3N4 Containing Al2O3 and Y2O3 during Sintering

Materials Science Forum ◽

10.4028/www.scientific.net/msf.561-565.577 ◽

2007 ◽

Vol 561-565 ◽

pp. 577-580 ◽

Cited By ~ 2

Author(s):

Ling Bai ◽

Chang Chun Ge ◽

Wei Ping Shen ◽

Ke Zhang ◽

X.D. Mao

Keyword(s):

Phase Transformation ◽

Silicon Nitride ◽

Precipitation Process ◽

Main Role ◽

Nitride Powder ◽

Densification Process ◽

Β Phase ◽

Α Phase ◽

Silicon Nitride Powder ◽

Si3n4 Ceramics

The densification and phase transformation of high α-phase silicon nitride powder synthesized by SHS with a combination of Y2O3 and Al2O3 sintering additives were investigated. The densification process occurred rapidly from 1400 to 1500 °C and was nearly finished at 1500 °C. However, the α-β transformation of silicon nitride progressed rapidly from 1500 to 1600 °C, and completed at 1600 °C. The phase transformation of silicon nitride lagged behind the densification of Si3N4 ceramics. It showed that the solution and precipitation process did not play the main role in the densification of silicon nitride. The sufficient amount of liquid phase was crucial to complete the densification.

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