Aerosol nanoparticles in the Fe1−xCrx system: Room-temperature stabilization of the σ phase and σ→α-phase transformation

Different factors calculated from theCcoefficients of the inherited orientation distribution function (ODF) allow us to check the importance of the variant selection. When no variant selection or a slight variant selection occurs by the cubic-to-hexagonal phase transformation, it is possible to calculate the ODF of the cubic parent phase present at high temperature from the ODF of the inherited hexagonal phase at room temperature. When a stronger variant selection occurs, qualitative information about the parent ODF can be obtained by using a specific correlation function, which we have named R(g).

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Effect of Al on Microstructures and Properties of Ti-45Al-8.5Nb-0.2B-0.2W Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.747-748.44 ◽

2013 ◽

Vol 747-748 ◽

pp. 44-49 ◽

Cited By ~ 2

Author(s):

Xiang Jun Xu ◽

Jun Pin Lin ◽

Dong Dong Han

Keyword(s):

Phase Transformation ◽

Room Temperature ◽

Optimal Combination ◽

Solidification Microstructure ◽

Processing Route ◽

Phase Transformation Temperature ◽

Compressive Properties ◽

Al Content ◽

Α Phase ◽

The Stability

In the present paper, the necessity of strictly controlling Al content is demonstrated for Ti-45Al-8.5Nb-0.2B-0.2W alloy by analyzing solidification microstructure, compressive properties at room temperature and α phase transformation point of alloys containing 43-47at.%Al. The results show that the alloy has an optimal combination of mechanical properties and microstructure. Increasing Al content leads to increase in lamellar colony size and decrease in B2 phase for the solidification microstructure. Yield strength decreases linearly with Al content, but total strain increases linearly with Al content. The phase transformation temperature of β + αα rises more than 20 °C when Al increases to 46at. %, and drops about 20 °C when Al decreases to 44at %. Therefore, Al deviation should be as small as possible in producing technical alloy to ensure the stability in terms of properties, microstructure and processing route.

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“Burst-like” Characteristics of the δ/α′ Phase Transformation in Pu-Ga Alloys

MRS Proceedings ◽

10.1557/proc-802-dd1.8 ◽

2003 ◽

Vol 802 ◽

Author(s):

Kerri J.M. Blobaum ◽

Christopher R. Krenn ◽

Jeffery J. Haslam ◽

Mark A. Wall ◽

Adam J. Schwartz

Keyword(s):

Phase Transformation ◽

Room Temperature ◽

Large Temperature ◽

Temperature Hysteresis ◽

Scanning Calorimetry ◽

Α Phase ◽

Δ Phase ◽

Annealing Cycle ◽

Heat Of Transformation ◽

Start Temperature

ABSTRACTThe δ to α′ phase transformation in Pu-Ga alloys is intriguing for both scientific and technological reasons. On cooling, the ductile fcc δ-phase transforms martensitically to the brittle monoclinic α′-phase at approximately −120°C (depending on composition). This exothermic transformation involves a 20% volume contraction and a significant increase in resistivity. The reversion of α′ to δ involves a large temperature hysteresis and begins just above room temperature. In an attempt to better understand the underlying thermodynamics and kinetics responsible for these unusual features, we are examining the δ/α' transformations in a Pu-0.6 wt% Ga alloy using differential scanning calorimetry (DSC) and resistometry. Both techniques indicate that the martensite start temperature is −120°C and the austenite start temperature is 35°C. The heat of transformation is approximately 3 kJ/mole. During the α ′ → δ reversion, “spikes” and “steps” are observed in DSC and resistometry scans, respectively. These spikes and steps are periodic, and their periodicity with respect to temperature does not vary with heating rate. With an appropriate annealing cycle, including a “rest” at room temperature, these spikes and steps can be reproduced through many thermal cycles of a single sample.

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Nanoindentation and Microstructure in the Shear Band in a Near Beta Titanium Alloy Ti-5Al-5Mo-5V-1Cr-1Fe

Materials ◽

10.3390/ma12244065 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4065

Author(s):

Bingfeng Wang ◽

Xu Ding ◽

Ying Mao ◽

Lanyi Liu ◽

Xiaoyong Zhang

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Titanium Alloy ◽

Phase Transformation ◽

Shear Band ◽

Cryogenic Temperature ◽

Room Temperature ◽

Beta Titanium Alloy ◽

Α Phase ◽

Beta Titanium

Shear localization is the main deformation mode for the near beta titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe loaded at high strain rates at either room temperature or cryogenic temperature. Nanoindentation, transmission electron microscopy, and high-resolution electron microscopy technique are applied to character the microstructure features and mechanical properties in the shear band of near beta titanium alloy. A white and straight band is observed in the shear region. Both microhardness and nanoindentaion hardness in the shear region are inferior to those in matrix. The different microstructure in the edge and the center in the shear band contribute to different mechanical properties. The plasticity of the entire shear band is almost homogenous when specimens are deformed at the cryogenic temperature. Rotational dynamic recrystallization is responsible for the formation of the ultrafine grains in the shear band. The edge of the shear band is composed of elongated grains, while there are ultrafine equiaxed grains in the center of the shear band. Deformation temperature has significant influence on the process of the grain refinement and the phase transformation in the shear band (SB). The grain sizes of the shear band in the specimen deformed at room temperature are larger than those in the specimens deformed at cryogenic temperature. The shear band consists of α phase grains in the specimen deformed at room temperature, and the shear band consists of α phase and lath-like α′ phase grains in the specimen deformed at cryogenic temperature. Finally, the mechanisms for phase transformation in the shear band are illustrated.

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Phase transformation and room temperature stabilization of various Bi2O3 nano-polymorphs: effect of oxygen-vacancy defects and reduced surface energy due to adsorbed carbon species

Nanoscale ◽

10.1039/d0nr06552h ◽

2020 ◽

Vol 12 (47) ◽

pp. 24119-24137

Author(s):

Ashish Chhaganlal Gandhi ◽

Chi-Yuan Lai ◽

Kuan-Ting Wu ◽

P. V. R. K. Ramacharyulu ◽

Valmiki B. Koli ◽

...

Keyword(s):

Phase Transformation ◽

Oxygen Vacancy ◽

Surface Energy ◽

Room Temperature ◽

Temperature Stabilization ◽

Red Emission ◽

Vacancy Defects ◽

Adsorbed Carbon ◽

Effect Of Oxygen ◽

Reduced Surface

The air annealing induced grain growth from nano to microscale and a transformation sequence from Bi → β-Bi2O3 → γ-Bi2O3 → α-Bi2O3 was evident. All the annealed samples are oxygen-deficient, resulting in the appearance of a strong red emission band.

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Mechanical Alloying Behavior in the Nb-Si, Ta-Si, and Nb-Ta-Si Systems

MRS Proceedings ◽

10.1557/proc-133-415 ◽

1988 ◽

Vol 133 ◽

Cited By ~ 3

Author(s):

K. S. Kumar ◽

S. K. Mannan

Keyword(s):

High Temperature ◽

Mechanical Alloying ◽

Mechanical Milling ◽

Room Temperature ◽

Crystalline Compound ◽

X Ray Diffraction ◽

X Ray ◽

Β Phase ◽

Α Phase

ABSTRACTThe mechanical alloying behavior of elemental powders in the Nb-Si, Ta-Si, and Nb-Ta-Si systems was examined via X-ray diffraction. The line compounds NbSi2 and TaSi2 form as crystalline compounds rather than amorphous products, but Nb5Si3 and Ta5Si3, although chemically analogous, respond very differently to mechanical milling. The Ta5Si3 composition goes directly from elemental powders to an amorphous product, whereas Nb5Si3 forms as a crystalline compound. The Nb5Si3 compound consists of both the tetragonal room-temperature α phase (c/a = 1.8) and the tetragonal high-temperature β phase (c/a = 0.5). Substituting increasing amounts of Ta for Nb in Nb5Si3 initially stabilizes the α-Nb5Si3 structure preferentially, and subsequently inhibits the formation of a crystalline compound.

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Effects of α–γ–α Phase Transformation on the ∑3 Boundaries in High-Purity Iron

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-05866-2 ◽

2021 ◽

Author(s):

Syed Ejaz Hussain ◽

Weiguo Wang ◽

Xinfu Gu ◽

Yunkai Cui ◽

Ahua Du ◽

...

Keyword(s):

Phase Transformation ◽

High Purity ◽

Α Phase ◽

Purity Iron ◽

High Purity Iron

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Phase Transformation of Kaolin-Ground Granulated Blast Furnace Slag from Geopolymerization to Sintering Process

Magnetochemistry ◽

10.3390/magnetochemistry7030032 ◽

2021 ◽

Vol 7 (3) ◽

pp. 32

Author(s):

Noorina Hidayu Jamil ◽

Mohd. Mustafa Al Bakri Abdullah ◽

Faizul Che Pa ◽

Mohamad Hasmaliza ◽

Wan Mohd Arif W. Ibrahim ◽

...

Keyword(s):

Phase Transformation ◽

Blast Furnace ◽

Blast Furnace Slag ◽

Room Temperature ◽

Curing Temperature ◽

Curing Process ◽

Sintering Process ◽

Granulated Blast Furnace Slag ◽

Fluxing Agent ◽

Furnace Slag

The main objective of this research was to investigate the influence of curing temperature on the phase transformation, mechanical properties, and microstructure of the as-cured and sintered kaolin-ground granulated blast furnace slag (GGBS) geopolymer. The curing temperature was varied, giving four different conditions; namely: Room temperature, 40, 60, and 80 °C. The kaolin-GGBS geopolymer was prepared, with a mixture of NaOH (8 M) and sodium silicate. The samples were cured for 14 days and sintered afterwards using the same sintering profile for all of the samples. The sintered kaolin-GGBS geopolymer that underwent the curing process at the temperature of 60 °C featured the highest strength value: 8.90 MPa, and a densified microstructure, compared with the other samples. The contribution of the Na2O in the geopolymerization process was as a self-fluxing agent for the production of the geopolymer ceramic at low temperatures.

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Oxygen Induced Phase Transformation in TC21 Alloy with a Lamellar Microstructure

Metals ◽

10.3390/met11010163 ◽

2021 ◽

Vol 11 (1) ◽

pp. 163

Author(s):

Shu Wang ◽

Yilong Liang ◽

Hao Sun ◽

Xin Feng ◽

Chaowen Huang

Keyword(s):

Electron Microscopy ◽

Phase Transformation ◽

Oxygen Uptake ◽

Titanium Alloys ◽

Electron Backscatter Diffraction ◽

Lamellar Microstructure ◽

Α Phase ◽

Transmission Electron ◽

The Matrix ◽

Oxygen Ingress

The main objective of the present study was to understand the oxygen ingress in titanium alloys at high temperatures. Investigations reveal that the oxygen diffusion layer (ODL) caused by oxygen ingress significantly affects the mechanical properties of titanium alloys. In the present study, the high-temperature oxygen ingress behavior of TC21 alloy with a lamellar microstructure was investigated. Microstructural characterizations were analyzed through optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Obtained results demonstrate that oxygen-induced phase transformation not only enhances the precipitation of secondary α-phase (αs) and forms more primary α phase (αp), but also promotes the recrystallization of the ODL. It was found that as the temperature of oxygen uptake increases, the thickness of the ODL initially increases and then decreases. The maximum depth of the ODL was obtained for the oxygen uptake temperature of 960 °C. In addition, a gradient microstructure (αp + β + βtrans)/(αp + βtrans)/(αp + β) was observed in the experiment. Meanwhile, it was also found that the hardness and dislocation density in the ODL is higher than that that of the matrix.

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X-Ray Investigations of the Low-Temperature Phases of the Organic Metals α- and β-(BEDT-TTF)2I3

Zeitschrift für Naturforschung A ◽

10.1515/zna-1986-1110 ◽

1986 ◽

Vol 41 (11) ◽

pp. 1319-1324 ◽

Cited By ~ 10

Author(s):

H. Endres ◽

H. J. Keller ◽

R. Swietlik ◽

D. Schweitzer ◽

K. Angermund ◽

...

Keyword(s):

Thermal Analysis ◽

Differential Thermal Analysis ◽

Room Temperature ◽

Unit Cell Volume ◽

Unit Cell ◽

Slight Variation ◽

X Ray ◽

Organic Metals ◽

Β Phase ◽

Α Phase

The structure of single crystals of the organic metals α- and β-(BEDT-TTF)2I3* was determined at 100 K, well below the phase transitions indicated by resistivity and thermopower measurements as well as by differential thermal analysis. In the α-phase no unusual change of the room temperature unit cell but a slight variation in the triiodide network and especially a more pronounced dimerization in one of the two donor stacks have been found. The β-phase develops a superstructure with a unit cell volume three times as large as that at room temperature and with pronounced distortions of the I3--ions.

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