Experimental Studies on Precursor Phenomena in Displacive Phase Transformations

1997 ◽  
pp. 321-332
Author(s):  
Dominique Schryvers
Keyword(s):  
Phase Transformations ◽  
Experimental Studies

scholarly journals Experimental and numerical studies of heat and mass transfer in low-temperature heat accumulator with phase transformations of accumulating material

2018 ◽  
Vol 240 ◽  
pp. 01009 ◽  
Author(s):  
Valery Gorobets ◽  
Ievgen Antypov ◽  
Viktor Trokhaniak ◽  
Yurii Bohdan
Keyword(s):  
Mass Transfer ◽  
Phase Transformations ◽  
Heat And Mass Transfer ◽  
Thermal Energy ◽  
Experimental Studies ◽  
Experimental Plant ◽  
Chemical Transformations ◽  
Heat Accumulator ◽  
Tube Bundles ◽  
Melting And Crystallization

Accumulation of thermal energy is produced with the aim of storing at certain times, when there is an overabundance of this energy and its further use in other periods of time when there is a deficit thermal energy. Thermal energy storage may be carried out under heating of any material (water, solid materials etc.) or by using the phase or chemical transformation of the material (melting and crystallization processes, direct and reverse chemical reaction). Thermal accumulators with phase or chemical transformations are allowed to concentrate a large amount of energy in a relatively small volume of accumulating material. In this paper an experimental study and numerical modeling of heat and mass transfer in the heat accumulator during phase transformations of the accumulating material are presented. The experimental plant consists of a chamber filled with paraffin. In experimental studies, the changes of the temperature distribution in heat accumulating material and tube bundles have investigated. Numerical simulation of melting and solidification of heat accumulating material during the heated and cooled of tube bundles were performed. As the results of research, the basic laws of melting and crystallization processes in heat accumulator during phase transformations of heat accumulating material were determined.

scholarly journals Numerical and Experimental Study of Phase Transformations in Welding Processes / Badania Numeryczne I Doświadczalne Przemian Fazowych W Procesach Spawania

2015 ◽  
Vol 60 (4) ◽  
pp. 2559-2568 ◽  
Author(s):  
W. Piekarska
Keyword(s):  
Solid State ◽  
Heat Source ◽  
Phase Transformations ◽  
High Speed ◽  
Numerical Models ◽  
Experimental Studies ◽  
Butt Joint ◽  
Heat Of Fusion ◽  
Large Temperature ◽  
Welding Processes

The paper concerns the mathematical and numerical modeling of phase transformations in solid state occurring during welding. The analysis of the influence of heating rate, cooling rate and maximum temperatures of thermal cycles on the kinetics of phase transformations is presented. On the basis of literature data and experimental studies the evaluation of classic mathematical and numerical models of phase transformation is presented with respect to the advanced methods of welding by using a high speed and a high power heat source. The prediction of the structure composition in laser welded butt-joint made of S460 steel is performed, where phase transformations are calculated on the basis of modified numerical models. Temperature distributions are determined as well as the shape and size of fusion zone and heat affected zone (HAZ). Temperature field is obtained by the solution of transient heat transfer equation with convective term and external volumetric heat source taken into account. Latent heat of fusion, evaporation and heats generated during phase transformations in solid state are considered in the numerical algorithm due to the large temperature range present in analyzed process. Results of the numerical prediction of structure composition in HAZ are presented in this work. Obtained results of computer simulations are compared to experimental research performered on the laser welded joint.

Experimental studies and thermodynamic simulation of phase transformations in high Nb containing γ-TiAl based alloys

2007 ◽  
Vol 98 (11) ◽  
pp. 1131-1137 ◽  
Author(s):  
Harald F. Chladil ◽  
Helmut Clemens ◽  
Gerald A. Zickler ◽  
Masao Takeyama ◽  
Ernst Kozeschnik ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Thermodynamic Simulation ◽  
Experimental Studies

Experimental Studies and Thermodynamic Simulations of Phase Transformations in Ti-(41-45)Al-4Nb-1Mo-0.1B Alloys

2008 ◽  
Vol 1128 ◽  
Author(s):  
Helmut Clemens ◽  
Barbara Boeck ◽  
Wilfried Wallgram ◽  
Thomas Schmoelzer ◽  
Laura M. Droessler ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transformations ◽  
Volume Fraction ◽  
Metastable Phase ◽  
Experimental Studies ◽  
High Energy ◽  
Thermodynamic Calculations ◽  
Transition Temperatures ◽  
High Concentration ◽  
Phase Transition Temperatures

AbstractTNM™ alloys are novel γ-TiAl based alloys which exhibit a high concentration of β-stabilizing elements such as Nb and Mo. Due to the high volume fraction of disordered β-phase these alloys can be hot-die forged under near conventional conditions. In this study, solid-state phase transformations and phase transition temperatures in Ti-(41-45)Al-4Nb-1Mo-0.1B (in at%) alloys were analyzed experimentally and compared to thermodynamic calculations. Results from scanning electron microscopy, conventional and high-energy X-ray diffraction as well as differential scanning calorimetry were used for the characterization of the prevailing phases and phase transformations. For the prediction of phase stabilities and phase transition temperatures thermodynamic calculations were conducted. ThermoCalc® was applied using a commercially available TiAl database. Combining all results a stable as well as a metastable phase diagram for Ti-(41-45)Al-4Nb-1Mo-0.1B alloys is proposed.

Stress-Strain State and Structural-Phase Transformations of Metal Articles Obtained by Laser Shaping

2021 ◽  
Vol 1038 ◽  
pp. 25-32
Author(s):  
Oleksii Kaglyak ◽  
Bohdan Romanov ◽  
Kateryna Romanova ◽  
Nataliia Tsapko
Keyword(s):  
Temperature Gradient ◽  
Phase Transformations ◽  
Structural Phase ◽  
Experimental Studies ◽  
Residual Austenite ◽  
Effect Of Temperature ◽  
Polymorphic Transformations ◽  
Irradiation Zone ◽  
Treatment Zone ◽  
Structural Phase Transformations

The article analyses the effect of temperature distribution at different points of the irradiation zone on the nature of leakage of structural-phase transformations. The results of the X-structural analysis are given, which shows the presence of martensite and residual austenite in the treatment zone. The peculiarities of structural-phase transformations during laser heating are studied and their effect on strain value during laser shaping is determined. The results of experimental studies are given, according to which, if the mechanisms for forming the temperature gradient and polymorphic transformations (for 65G steel) operate in parallel, the amount of deformation is one third of the sample for which only the temperature gradient mechanism works (12Х18N10Т steel).

Experimental Studies of Phase Transformations in a Carbon Containing Ti-45Al-7.5Nb Alloy and Related Thermodynamic Simulations

2005 ◽  
Vol 7 (12) ◽  
pp. 1131-1134 ◽  
Author(s):  
H. F. Chladil ◽  
H. Clemens ◽  
H. Leitner ◽  
A. Bartels ◽  
R. Gerling ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Experimental Studies ◽  
Thermodynamic Simulations

Experimental Studies and Thermodynamic Simulation of Phase Transformations in γ-TiAl Based Alloys

2004 ◽  
Vol 842 ◽  
Author(s):  
Harald F. Chladil ◽  
Helmut Clemens ◽  
Harald Leitner ◽  
Arno Bartels ◽  
Rainer Gerling ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Thermodynamic Simulation ◽  
Experimental Studies ◽  
Transition Temperatures ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Thermodynamic Simulations ◽  
Simulation Based ◽  
Phase Transition Temperatures

ABSTRACTPhase transformations and phase transition temperatures in several Nb-rich γ-TiAl based alloys were investigated experimentally and compared to thermodynamic simulations. The present study combines light-optical and scanning electron microscopy, X-ray diffraction and differential-scanning-calorimetry for the characterization of the prevailing phases and phase transformations. Thermodynamic simulation based on the CALPHAD method was used for predict phase stabilities. The results from experiments on a variety of γ-TiAl based alloys are compared to thermodynamic calculations. Finally, the influence of carbon on the transition temperatures is presented.

3-D reconstruction and analysis of mammalian mitotic spindle structure

1992 ◽  
Vol 50 (1) ◽  
pp. 578-579
Author(s):  
Kent McDonald ◽  
David Mastronarde ◽  
Rubai Ding ◽  
Eileen O'Toole ◽  
J. Richard McIntosh
Keyword(s):  
Cross Sections ◽  
Mitotic Spindle ◽  
Experimental Studies ◽  
Video Camera ◽  
Three Dimensions ◽  
Mitotic Spindles ◽  
Black And White ◽  
Reconstruction Methods ◽  
Spindle Structure ◽  
Tissue Culture Line

Mammalian spindles are generally large and may contain over a thousand microtubules (MTs). For this reason they are difficult to reconstruct in three dimensions and many researchers have chosen to study the smaller and simpler spindles of lower eukaryotes. Nevertheless, the mammalian spindle is used for many experimental studies and it would be useful to know its detailed structure.We have been using serial cross sections and computer reconstruction methods to analyze MT distributions in mitotic spindles of PtK cells, a mammalian tissue culture line. Images from EM negatives are digtized on a light box by a Dage MTI video camera containing a black and white Saticon tube. The signal is digitized by a Parallax 1280 graphics device in a MicroVax III computer. Microtubules are digitized at a magnification such that each is 10-12 pixels in diameter.

The use of high-resolution FESEM to study solid-state phase transformations and reactions

1994 ◽  
Vol 52 ◽  
pp. 1028-1029
Author(s):  
P. G. Kotula ◽  
D. D. Erickson ◽  
C. B. Carter
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Phase Transformations ◽  
High Efficiency ◽  
Sol Gel ◽  
Quantitative Information ◽  
Solid State Reactions ◽  
Critical Dimensions ◽  
Backscattered Electrons ◽  
Backscattered Electron

High-resolution field-emission-gun scanning electron microscopy (FESEM) has recently emerged as an extremely powerful method for characterizing the micro- or nanostructure of materials. The development of high efficiency backscattered-electron detectors has increased the resolution attainable with backscattered-electrons to almost that attainable with secondary-electrons. This increased resolution allows backscattered-electron imaging to be utilized to study materials once possible only by TEM. In addition to providing quantitative information, such as critical dimensions, SEM is more statistically representative. That is, the amount of material that can be sampled with SEM for a given measurement is many orders of magnitude greater than that with TEM.In the present work, a Hitachi S-900 FESEM (operating at 5kV) equipped with a high-resolution backscattered electron detector, has been used to study the α-Fe2O3 enhanced or seeded solid-state phase transformations of sol-gel alumina and solid-state reactions in the NiO/α-Al2O3 system. In both cases, a thin-film cross-section approach has been developed to facilitate the investigation. Specifically, the FESEM allows transformed- or reaction-layer thicknesses along interfaces that are millimeters in length to be measured with a resolution of better than 10nm.

The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film

1993 ◽  
Vol 51 ◽  
pp. 842-843
Author(s):  
K. Barmak
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Phase Transformations ◽  
Analytical Electron Microscopy ◽  
Ex Situ ◽  
Multilayer Thin Films ◽  
Absolute Concentration ◽  
Analytical Electron ◽  
Deposition Step

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.

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