scholarly journals A New Method for Determining the Brittle-to-Ductile Transition Temperature of a TiAl Intermetallic

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1550
Author(s):  
Sarper Nizamoglu ◽  
Karl-Heinz Lang ◽  
Stefan Guth ◽  
Martin Heilmaier
Keyword(s):  
Transition Temperature ◽  
Charpy Impact ◽  
Plastic Strain Amplitude ◽  
Bending Tests ◽  
Brittle To Ductile Transition ◽  
Intermetallic Materials ◽  
Different Temperatures ◽  
Specific Temperature ◽  
Increasing Temperature ◽  
Fully Lamellar

Intermetallic materials typically change their deformation behavior from brittle to ductile at a certain temperature called the Brittle-to-Ductile Transition Temperature (BDTT). This specific temperature can be determined by the Charpy impact, tensile or bending tests conducted at different temperatures and strain rates, which usually requires a large number of specimens. In order to reduce the number of necessary specimens for finding the BDTT, a new methodology comprising cyclic loadings as the crucial step was studied on a fully lamellar TiAl alloy with composition Ti-48Al-2Nb-0.7Cr-0.3Si. The loading blocks are applied isothermally under strain control and repeated on the same specimen at different temperatures. The development of plastic strain amplitude with increasing temperature is analyzed to determine the BDTT of the specimen. The BDTTs found with the described method agree well with literature data derived with conventional methods. With the loading strategy presented in this study, the BDTT and additionally the effect of strain rate on it can be found by using a single specimen.

Microstructure-Toughness Relationship in AISI4340 Steel

2011 ◽  
Vol 312-315 ◽  
pp. 110-115
Author(s):  
N. Saeidi ◽  
A. Ekrami
Keyword(s):  
Transition Temperature ◽  
Charpy Impact ◽  
Brittle Transition ◽  
Hardness Tests ◽  
Ductile Brittle Transition Temperature ◽  
Different Temperatures ◽  
Ferrite Steel ◽  
Brittle Transition Temperature ◽  
Impact Data ◽  
Aisi4340 Steel

To improve the strength and toughness of AISI 4340 steel, different microstructures, containing full bainite, bainite-ferrite, martensite-ferrite and full martensite were produced by different heat treatment cycles. Tensile, impact and hardness tests were carried out at room temperature. The ductile-brittle transition temperature was determined from impact data at different temperatures. The results showed that steel with bainite - 0.34 ferrite microstructure has the highest elongation and charpy impact energy, while its tensile strength and yield stress decreased in comparison to other microstructures. This increment was noticeable when bainite - 0.34 ferrite steel was tempered. The ductile-brittle transition temperature decreased with tempering of bainite -0.34 steel. The fracture surface analysis of charpy specimens also showed an increase in toughness of tempered bainite-ferrite in comparison to other microstructures.

Mechanical Properties Distribution in Welds and Forging of VVER-1000

2009 ◽  
Author(s):  
Anna A. Chernobaeva ◽  
Natalya A. Shulgan ◽  
Yaroslav I. Shtrombakh ◽  
Tatyana I. Titova ◽  
Yury A. Nikolaev ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Weld Metal ◽  
Base Metal ◽  
Axial Direction ◽  
Testing Procedure ◽  
Bending Tests ◽  
Brittle To Ductile Transition ◽  
Conservative Estimation ◽  
Surveillance Specimens ◽  
Values Distribution

Study of weld metal and shell metal of VVER-1000 reactor is carried out. Metal of the control welded joint performed to the welds Nos. 3 and 4 and metal of the test ring of supporting shell is used. For each of the analyzed materials the bending tests of Charpy specimens are carried out according to the surveillance specimens testing procedure. Fabrication of specimens and all the tests are performed by TK “OMZ Izhora”, ltd. Leadership of the tests and assessment of brittle-to-ductile transition temperature is performed by RRC “Kurchatov Institute”. It is shown that guaranteed values of brittle-to-ductile transition temperature (TK0) for VVER-1000 pressure vessel materials (0°C for weld and −25°C for base metal [1]) are the conservative estimation of TK values obtained for all groups of the tested specimens. However in some cases such estimation is super conservative. Assessment of distribution of brittle-to-ductile transition temperature (TK) values of the weld in radial direction has shown that TK varies from layer to layer in the range from −55 to −22°C. Variations of TK values are conceivably random and not connected with changes of the chemical composition of metal. It is shown that the situation is possible when brittle-to-ductile transition temperature of “inner grooving” weld metal is higher than that of the “outer grooving” weld metal. This result should be taken into account when planning the surveillance specimens programmes. Metal of “inner grooving” should be included in surveillance specimens. While assessing the TK values distribution in axial direction it has been determined that the maximum brittle-to-ductile transition temperature is specific for the area adjacent to the line of weld-to-base metal alloying. This effect is stably observed already at a distance of 8 mm from the alloying line. Study of distribution of TK values of supporting shell metal has shown that for the analyzed supporting shell the maximum brittle-to-ductile transition temperature value corresponds to the inner side of the shell middle third, the minimum value — to the shell inner surface. On the whole, shell metal is characterized by rather low values of brittle-to-ductile transition temperature.

Investigation of Influence of Quenching and Annealing on the Plane Fracture Toughness and Brittle to Ductile Transition Temperature of the Zinc Coated Structural Steel Materials

2017 ◽  
Vol 5 (2) ◽  
pp. 33-42
Author(s):  
M. Ramesh ◽  
Rajnish Garg ◽  
Garimella V. Subrahmanyam
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Transition Temperature ◽  
Structural Steel ◽  
Water Quenching ◽  
Time Interval ◽  
Brittle To Ductile Transition ◽  
Treatment Processes ◽  
Specific Temperature

This article discusses that the variation in fracture toughness is exclusively due to the influence of coating on the surface of the material, depending upon the time interval that the specimen is immersed in the coating tub under a specific temperature. Parameters during the process of coating have shown their own influence on heat treatment, which has shown its own significance of the fracture toughness of coated and uncoated materials. Hence, to estimate this effect, EN 18 and AISI 1020 steels have been tested under different heat treatment processes, like annealing, oil-quenching and water-quenching. The results obtained under these conditions have clearly shown that the influence of heat treatment is significant on the fracture toughness of the materials. Compared to untreated materials, the annealed and quenched materials have shown much variation in fracture toughness.

High Temperature Fracture Toughness in Silicon Nitride and Sialon

1993 ◽  
Vol 115 (3) ◽  
pp. 268-272 ◽  
Author(s):  
Y. Mutoh ◽  
N. Miyahara ◽  
K. Yamaishi ◽  
T. Oikawa
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Transition Temperature ◽  
Silicon Nitride ◽  
Glass Phase ◽  
Temperature Transition ◽  
Brittle To Ductile Transition ◽  
Temperature Fracture ◽  
Increasing Temperature ◽  
Sintered Silicon

Fracture Toughness of HIP-sintered silicon nitride decreased with increasing temperature up to 1200°C. The brittle-to-ductile transition was observed in the temperature range from 1200°C to 1275°C: the fracture toughness rapidly increased in the transition region. Above the transition temperature, the fracture toughness decreased with increasing temperature. Fracture toughness of sialon increased with increasing temperature. Transition of fracture mechanism was observed in sialon around 1300°C. The differences of temperature dependence of fracture toughness between two materials are interpreted in terms of the effects of grain-boundary glass phase on fracture.

Study on Friction Coefficient between Carbon/Epoxy Composites and a Monocrystalline Diamond under Different Temperatures

2012 ◽  
Vol 565 ◽  
pp. 627-632 ◽  
Author(s):  
Ben Wang ◽  
Hang Gao ◽  
Song Peng Zhang ◽  
Yong Jie Bao
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Friction Coefficient ◽  
Epoxy Resin ◽  
Cutting Tool ◽  
Epoxy Composites ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Monocrystalline Diamond

The main source of heat generation during machining of carbon/epoxy composites is the friction among cutting tool, chip and workpiece. The friction coefficient between carbon/epoxy composites and a monocrystalline diamond under different temperatures was investigated. The results show that the friction coefficient between diamond and carbon/epoxy composites changes with the variation of temperature due to the change of properties of epoxy resin. The friction coefficient increases with the increasing temperature. However, when the temperature of workpiece was higher than the glass transition temperature of epoxy resin, the friction coefficient decreased.

The structure of membranes and membrane proteins embedded in amorphous ice

1992 ◽  
Vol 50 (1) ◽  
pp. 432-433
Author(s):  
Uwe Lücken ◽  
Joachim Jäger
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Vesicles ◽  
Freezing Stress ◽  
Amorphous Ice ◽  
Different Temperatures ◽  
Band Pass ◽  
Lipid Polymorphism

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.

scholarly journals A Comparative Electrochemical and Morphological Investigation on the Behavior of NiCr and CoCr Dental Alloys at Various Temperatures

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 256
Author(s):  
Florentina Golgovici ◽  
Mariana Prodana ◽  
Florentina Gina Ionascu ◽  
Ioana Demetrescu
Keyword(s):  
Low Temperatures ◽  
Artificial Saliva ◽  
Electrochemical Stability ◽  
Morphological Investigation ◽  
Dental Alloys ◽  
Ion Release ◽  
Icp Ms ◽  
Different Temperatures ◽  
Good Concordance ◽  
Increasing Temperature

The purpose of our study is to compare the behavior of two reprocessed dental alloys (NiCr and CoCr) at different temperatures considering the idea that food and drinks in the oral cavity create various compositions at different pH levels; the novelty is the investigation of temperature effect on corrosion parameters and ion release of dental alloys. Electrochemical stability was studied together with morphology, elemental composition and ions release determination. The results obtained are in good concordance: electrochemistry studies reveal that the corrosion rate is increasing by increasing the temperature. From SEM coupled with EDS, the oxide film formed on the surface of the alloys is stable at low temperatures and a trend to break after 310K. ICP-MS results evidence that in accordance with increasing temperature, the quantities of ions released from the alloys immersed in artificial saliva also increase, though they still remain small, less than 20 ppm.

scholarly journals Simulation of FDSOI-ISFET with Tunable Sensitivity by Temperature and Dual-Gate Structure

Electronics ◽  
2021 ◽  
Vol 10 (13) ◽  
pp. 1585
Author(s):  
Hanbin Wang ◽  
Jinshun Bi ◽  
Mengxin Liu ◽  
Tingting Han
Keyword(s):  
Gate Voltage ◽  
Computer Aided Design ◽  
Silicon On Insulator ◽  
Fully Depleted ◽  
Gate Structure ◽  
Different Temperatures ◽  
Dual Gate ◽  
Sensitivity Changes ◽  
Increasing Temperature ◽  
Aided Design

This work investigates the different sensitivities of an ion-sensitive field-effect transistor (ISFET) based on fully depleted silicon-on-insulator (FDSOI). Using computer-aided design (TCAD) tools, the sensitivity of a single-gate FDSOI based ISFET (FDSOI-ISFET) at different temperatures and the effects of the planar dual-gate structure on the sensitivity are determined. It is found that the sensitivity increases linearly with increasing temperature, reaching 890 mV/pH at 75 °C. By using a dual-gate structure and adjusting the control gate voltage, the sensitivity can be reduced from 750 mV/pH at 0 V control gate voltage to 540 mV/pH at 1 V control gate voltage. The above sensitivity changes are produced because the Nernst limit changes with temperature or the electric field generated by different control gate voltages causes changes in the carrier movement. It is proved that a single FDSOI-ISFET can have adjustable sensitivity by adjusting the operating temperature or the control gate voltage of the dual-gate device.

scholarly journals Correlation and prediction of solubility of hydrogen in alkenes and its dissolution properties

2021 ◽  
Author(s):  
Mohammad Jamali ◽  
Amir Abbas Izadpanah ◽  
Masoud Mofarahi
Keyword(s):  
Equation Of State ◽  
Binary Interaction ◽  
Absolute Deviation ◽  
Dissolution Properties ◽  
Different Temperatures ◽  
Binary Interaction Parameters ◽  
Delta G ◽  
Hoff Equation ◽  
Increasing Temperature ◽  
Total Average

AbstractIn this work, solubility of hydrogen in some alkenes was investigated at different temperatures and pressures. Solubility values were calculated using the Peng–Robinson equation of state. Binary interaction parameters were calculated using fitting the equation of state on experimental data, Group contribution method and Moysan correlations and total average absolute deviation for these methods was 3.90, 17.60 and 13.62, respectively. Because hydrogen solubility in Alkenes is low, Henry’s law for these solutions were investigated, too. Results of calculation showed with increasing temperature, Henry’s constant was decreased. The temperature dependency of Henry’s constants of hydrogen in ethylene and propylene was higher than to other alkenes. In addition, using Van’t Hoff equation, the thermodynamic parameters for dissolution of hydrogen in various alkenes were calculated. Results indicated that the dissolution of hydrogen was spontaneous and endothermic. The total average of dissolution enthalpy ($${\Delta H}^{^\circ }$$ Δ H ∘ ) and Gibbs free energy ($${\Delta G}^{^\circ }$$ Δ G ∘ ) for these systems was 3.867 kJ/mol and 6.361 kJ/mol, respectively. But dissolution of hydrogen in almost of alkenes was not an entropy-driven process.

Temperature Dependence of Hole Impact Ionization Coefficient in 4H-SiC Photodiodes

2009 ◽  
Vol 615-617 ◽  
pp. 311-314 ◽  
Author(s):  
W.S. Loh ◽  
J.P.R. David ◽  
B.K. Ng ◽  
Stanislav I. Soloviev ◽  
Peter M. Sandvik ◽  
...  
Keyword(s):  
Phonon Scattering ◽  
Impact Ionization ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Different Temperatures ◽  
Ionization Coefficients ◽  
Increasing Temperature ◽  
The Impact ◽  
Good Agreement ◽  
Ionization Rates

Hole initiated multiplication characteristics of 4H-SiC Separate Absorption and Multiplication Avalanche Photodiodes (SAM-APDs) with a n- multiplication layer of 2.7 µm were obtained using 325nm excitation at temperatures ranging from 300 to 450K. The breakdown voltages increased by 200mV/K over the investigated temperature range, which indicates a positive temperature coefficient. Local ionization coefficients, including the extracted temperature dependencies, were derived in the form of the Chynoweth expression and were used to predict the hole multiplication characteristics at different temperatures. Good agreement was obtained between the measured and the modeled multiplication using these ionization coefficients. The impact ionization coefficients decreased with increasing temperature, corresponding to an increase in breakdown voltage. This result agrees well with the multiplication characteristics and can be attributed to phonon scattering enhanced carrier cooling which has suppressed the ionization process at high temperatures. Hence, a much higher electric field is required to achieve the same ionization rates.

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