Microstructure and Thermal Stability of Copper - Carbon Nanotube Composites Consolidated by High Pressure Torsion

2012 ◽  
Vol 729 ◽  
pp. 228-233 ◽  
Author(s):  
P. Jenei ◽  
E.Y. Yoon ◽  
Jenő Gubicza ◽  
Hyoung Seop Kim ◽  
J.L. Lábár ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
High Pressure ◽  
Dislocation Density ◽  
High Pressure Torsion ◽  
Lattice Defect ◽  
Taylor Formula ◽  
Processing Temperature ◽  
Pure Cu ◽  
Thermal Stability Of

Blends of Cu powders and 3 vol. % carbon nanotubes (CNTs), and an additional sample from pure Cu powder were consolidated by High Pressure Torsion (HPT) at room temperature (RT) and 373 K. The grain size, the lattice defect densities as well as the hardness of the pure and composite materials were determined. Due to the pinning effect of CNTs, the dislocation density is about three times larger, while the grain size is about half of that obtained in the sample consolidated from the pure Cu powder. The increase of the HPT-processing temperature from RT to 373 K resulted in only a slight increase of the grain size in the Cu-CNT composite while the dislocation density and the twin boundary frequency were reduced significantly. The flow stress obtained experimentally agrees well with the value calculated by the Taylor-formula indicating that the strength in both pure Cu and Cu-CNT composites is determined mainly by the interaction between dislocations. The addition of CNTs to Cu yields a significantly better thermal stability of the UFG matrix processed by HPT.

Thermal Stability of Ultrafine-Grained Pure Titanium Processed by High-Pressure Torsion

2021 ◽  
Vol 1016 ◽  
pp. 338-344
Author(s):  
Wan Ji Chen ◽  
Jie Xu ◽  
De Tong Liu ◽  
De Bin Shan ◽  
Bin Guo ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Grain Size ◽  
High Pressure ◽  
Annealing Temperature ◽  
High Pressure Torsion ◽  
Stored Energy ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Thermal Stability Of

High-pressure torsion (HPT) was conducted under 6.0 GPa on commercial purity titanium up to 10 turns. An ultrafine-grained (UFG) pure Ti with an average grain size of ~96 nm was obtained. The thermal properties of these samples were studied by using differential scanning calorimeter (DSC) which allowed the quantitative determination of the evolution of stored energy, the recrystallization temperatures, the activation energy involved in the recrystallization of the material and the evolution of the recrystallized fraction with temperature. The results show that the stored energy increases, beyond which the stored energy seems to level off to a saturated value with increase of HPT up to 5 turns. An average activation energy of about 101 kJ/mol for the recrystallization of 5 turns samples was determined. Also, the thermal stability of the grains of the 5 turns samples with subsequent heat treatments were investigated by microstructural analysis and Vickers microhardness measurements. It is shown that the average grain size remains below 246 nm when the annealing temperature is below 500 °C, and the size of the grains increases significantly for samples at the annealing temperature of 600 °C.

scholarly journals Thermal stability of a nanocrystalline HfNbTiZr multi-principal element alloy processed by high-pressure torsion

2020 ◽  
Vol 168 ◽  
pp. 110550 ◽  
Author(s):  
Pham Tran Hung ◽  
Megumi Kawasaki ◽  
Jae-Kyung Han ◽  
János L. Lábár ◽  
Jenő Gubicza
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Principal Element ◽  
Thermal Stability Of

Thermal stability of pure bcc Zr fabricated by high pressure torsion

2010 ◽  
Vol 64 (2) ◽  
pp. 211-214 ◽  
Author(s):  
M.T. Pérez-Prado ◽  
A. Sharafutdinov ◽  
A.P. Zhilyaev
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Thermal Stability Of

scholarly journals Improved Hardness and Thermal Stability of Nanocrystalline Nickel Electrodeposited with the Addition of Cysteine

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2254
Author(s):  
Tamás Kolonits ◽  
Zsolt Czigány ◽  
László Péter ◽  
Imre Bakonyi ◽  
Jenő Gubicza
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Dislocation Density ◽  
Nickel Sulfate ◽  
Fault Probability ◽  
Nanocrystalline Nickel ◽  
Twin Fault ◽  
Cysteine Content ◽  
Heating Up ◽  
Thermal Stability Of

Experiments were conducted for the study of the effect of cysteine addition on the microstructure of nanocrystalline Ni films electrodeposited from a nickel sulfate-based bath. Furthermore, the thermal stability of the nanostructure of Ni layers processed with cysteine addition was also investigated. It was found that with increasing cysteine content in the bath, the grain size decreased, while the dislocation density and the twin fault probability increased. Simultaneously, the hardness increased due to cysteine addition through various effects. Saturation in the microstructure and hardness was achieved at cysteine contents of 0.3–0.4 g/L. Moreover, the texture changed from (220) to (200) with increasing the concentration of cysteine. The hardness of the Ni films processed with the addition of 0.4 g/L cysteine (∼6800 MPa) was higher than the values obtained for other additives in the literature (<6000 MPa). This hardness was further enhanced to ∼8400 MPa when the Ni film was heated up to 500 K. It was revealed that the hardness remained as high as 6000 MPa even after heating up to 750 K, while for other additives, the hardness decreased below 3000 MPa at the same temperature.

scholarly journals Formation and Thermal Stability of ω-Ti(Fe) in α-Phase-Based Ti(Fe) Alloys

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 402 ◽  
Author(s):  
Mario J. Kriegel ◽  
Martin Rudolph ◽  
Askar Kilmametov ◽  
Boris B. Straumal ◽  
Julia Ivanisenko ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
High Temperatures ◽  
High Pressure Torsion ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Phase Assemblage ◽  
Two Phase ◽  
High Temperature Xrd ◽  
Thermal Stability Of

In this work, the formation and thermal stability of the ω-Ti(Fe) phase that were produced by the high-pressure torsion (HPT) were studied in two-phase α-Ti + TiFe alloys containing 2 wt.%, 4 wt.% and 10 wt.% iron. The two-phase microstructure was achieved by annealing the alloys at 470 °C for 4000 h and then quenching them in water. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were utilized to characterize the samples. The thermal stability of the ω-Ti(Fe) phase was investigated using differential scanning calorimetry (DSC) and in situ high-temperature XRD. In the HPT process, the high-pressure ω-Ti(Fe) phase mainly formed from α-Ti. It started to decompose by a cascade of exothermic reactions already at temperatures of 130 °C. The decomposition was finished above ~320 °C. Upon further heating, the phase transformation proceeded via the formation of a supersaturated α-Ti(Fe) phase. Finally, the equilibrium phase assemblage was established at high temperatures. The eutectoid temperature and the phase transition temperatures measured in deformed and heat-treated samples are compared for the samples with different iron concentrations and for samples with different phase compositions prior to the HPT process. Thermodynamic calculations were carried out to predict stable and metastable phase assemblages after heat-treatments at low (α-Ti + TiFe) and high temperatures (α-Ti + β-(Ti,Fe), β-(Ti,Fe)).

ANALYSIS OF THE THERMAL STABILITY OF COPPER SPECIMENS DEFORMED BY HIGH--PRESSURE TORSION

2010 ◽  
Vol 46 (4) ◽  
pp. 458-465 ◽  
Author(s):  
Ziling XIE ◽  
Xiaolei WU ◽  
Jijia XIE ◽  
Youshi HONG
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Thermal Stability Of
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