scholarly journals Creep Behavior of Near α High Temperature Ti-6.6Al-4.6Sn-4.6Zr-0.9Nb-1.0Mo-0.32Si Alloy

2021 ◽  
Vol 8 ◽  
Author(s):  
Dongye Yang ◽  
Wenqi Tian ◽  
Xinqi Zhang ◽  
Ke Si ◽  
Jiuxiao Li
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Creep Mechanism ◽  
Creep Properties ◽  
Microstructure Characteristics ◽  
Transmission Electron ◽  
Diffusion Controlled ◽  
Dislocation Movement ◽  
Alloy Microstructure ◽  
Applied Stresses

This study focuses on the microstructure characteristics and tensile and creep properties of a near α high temperature Ti-6.6Al-4.6Sn-4.6Zr-0.9Nb-1.0Mo-0.32Si alloy. Microstructure characteristics were quantitatively investigated using optical microscopy, scanning electron microscope, and transmission electron microscopy. Tensile properties were carried out at room and high temperature. Creep properties were detected under applied stresses ranging from 100–350 MPa at 873–973 K, respectively. Results showed that Widmanstätten microstructure was obtained after hot forged and heat treatment. The strength decreases and the elongation rises with temperature increasing. The ultimate strength and elongation were 1010 MPa, 12% at room temperature, and 620 MPa, 20% at 923 K, respectively. The steady state creep rates rise correspondingly with stress and temperature. Stress exponents are measured within the range of 3.0–3.5. Thus, the creep mechanism is diffusion-controlled viscous glide of dislocation. Ti3Al precipitates are observed. The boundaries and precipitates can obstruct dislocation movement to improve the creep properties. Fracture mechanism of creep is intergranular. The creep mechanism varied from climb of dislocation to sliding of dislocation solution.

The High Temperature Creep Behavior of Mg-5Li-3Al-2Zn-2Cu Alloy

2013 ◽  
Vol 760-762 ◽  
pp. 759-762
Author(s):  
Ting Qu Li ◽  
Xiang Ling Liu ◽  
Zhan Yi Cao
Keyword(s):  
Creep Behavior ◽  
Room Temperature ◽  
Microstructural Analysis ◽  
Dislocation Creep ◽  
High Temperature Creep ◽  
Creep Properties ◽  
X Ray ◽  
Transmission Electron ◽  
The Matrix ◽  
Dislocation Movement

The room-temperature mechanical properties of the extruded Mg-5Li-3Al-2Zn-2Cu alloy (LAZ532-2Cu) were researched previously. In this paper, the creep behavior of the extruded LAZ532-2Cu alloy was studied at the temperature range from 398K to 448K, with the stress 60MPa, 80MPa and 100MPa. The microstructure of the alloy consists of the matrix α-Mg solid solution and the intermetallic compounds on the grain boundary or in the grain. The microstructural analysis of the alloy reveals the correlation between microstructure and creep properties. The stress exponent n 3.72, 4.8, 6.1, the activation energy Qc 94.8kJ/mol, 123.9kJ/mol, 128 kJ/mol were calculated at the test condition. The creep test samples were combined with detailed transmission electron microscopy and X-ray diffractometry in order to characterize the precipitated AlLi phase, which contributes to the creep resistance by obstructing the dislocation movement in dislocation creep.

Observation of Ag Precipitate in CuAgZr Alloy during In Situ High Temperature TEM

2017 ◽  
Vol 263 ◽  
pp. 50-54
Author(s):  
Waraporn Piyawit ◽  
Panya Buahombura
Keyword(s):  
High Temperature ◽  
Heating Process ◽  
Minor Variation ◽  
Transmission Electron ◽  
Large Lattice ◽  
Dislocation Movement ◽  
Higher Temperature ◽  
Average Size ◽  
A Minor

CuAgZr alloy is a minor variation of CuAg alloy that is remarkably known for good combination of strength and electrical conductivity. Strengthening and conductivity enhancing of CuAgZr alloy is essentially proficient by the precipitation of Ag precipitates. The behavior of Ag precipitates at high temperature was investigated using in-situ transmission electron microscopy. These nanoscale Ag precipitates are formed in CuAgZr alloy during heating process with the average size of 5 nm. Growth of precipitates at higher temperature can be explained by the consumption of solute diffusing from smaller precipitates. Dislocation looping at high temperature would be the effects of a large lattice strain along matrix/precipitate interface that would retard the dislocation movement.

High-Temperature Mechanical Properties of Al2O3/Ti3SiC2 Multilayer Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 1877-1880 ◽  
Author(s):  
Qing Feng Zan ◽  
Chang An Wang ◽  
Li Min Dong ◽  
Yong Huang
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Room Temperature ◽  
Diffusion Creep ◽  
Creep Function ◽  
High Temperature Mechanical Properties ◽  
Multilayer Composites ◽  
Dislocation Movement ◽  
Monolithic Ceramics ◽  
Multilayer Materials

The high-temperature mechanical properties were very important to structural materials, especially structural ceramics. Hence, the strength, elastic modulus, stress relaxation and creep behavior of the multilayer materials at elevated temperature were studied in this paper. According to the curves of mechanical properties varieties with temperature risen from room-temperature to 1300°C, the multilayer materials could remain relatively high mechanical properties until 1150°C. Otherwise, the creep function of the multilayer composites was also determined, in which the stress exponent was 1.4 and activation energy was 204kJ/mol. By contrasting to the monolithic ceramics of Al2O3 and Ti3SiC2, the main creep mechanisms include: interface diffusion creep (in Al2O3 layers), dislocation movement creep, grain delamination and sliding (in Ti3SiC2 layers).

scholarly journals Microstructural evolution and Mechanical Properties of a Newly Developed Ti2AlNb-based alloy

2020 ◽  
Vol 321 ◽  
pp. 11064
Author(s):  
Yongsheng HE ◽  
Wenzhong LUO ◽  
Yujun DU ◽  
Ming WU ◽  
Kaixuan Wang ◽  
...  
Keyword(s):  
Tensile Strength ◽  
High Temperature ◽  
Room Temperature ◽  
Phase Region ◽  
High Plasticity ◽  
Phase Zone ◽  
Creep Properties ◽  
Three Phase ◽  
High Temperature Tensile ◽  
High Temperature Tensile Properties

The effects of the microstructure on the tensile and creep properties of the alloy at room temperature and high temperature were investigated by controlling the microstructures of the alloy by different hot working processes. It is found that the lath microstructure obtained by forging in B2 single phase zone has high tensile strength. The tensile strength is 1188 MPa at room temperature and 950 MPa at high temperature. The equiaxed structure obtained by forging in O+B2 phase region has the characteristics of high plasticity, creep resistance and low tensile strength. The elongation at room temperature is 9.0%, and the elongation at high temperature is 36%. The ambient temperature, high temperature tensile properties of the dual microstructure obtained by forging in the three-phase zone of α2+O+B2 are between the lath and the equiaxed microstructure.

Dynamic Behavior of a Silicon Oxide Layer on Silicon Ultrafine Particles

2003 ◽  
Vol 10 (02n03) ◽  
pp. 361-364
Author(s):  
Yuki Kimura ◽  
Hiroshi Ueno ◽  
Hitoshi Suzuki ◽  
Takeshi Sato ◽  
Toshiaki Tanigaki ◽  
...  
Keyword(s):  
High Temperature ◽  
Oxide Layer ◽  
Ultrafine Particles ◽  
Room Temperature ◽  
Silicon Oxide ◽  
Silicon Oxide Layer ◽  
Transmission Electron ◽  
Natural Oxide ◽  
High Temperature Stage ◽  
Amorphous Silicon Oxide

In order to clarify the high-temperature behavior of a silicon oxide layer on the surface of Si ultrafine particles, the oxide layer has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. The natural oxide layer grown on Si ultrafine particles by exposure to air was an amorphous silicon oxide layer with a thickness of 1.5 nm. This oxide layer started to dissolve into the Si crystal upon heating at 500°C, and was fully dissolved into the Si crystal at 600°C in vacuum. When the specimen was cooled back to room temperature, the silicon oxide layer reappeared on the Si surface. This phenomenon, which can be detected only at high temperatures, is presented in this paper.

A Study on Microstructures and Creep Behaviors in the Mg-3Sr-xY Alloys

2011 ◽  
Vol 418-420 ◽  
pp. 602-605
Author(s):  
Ming Hu ◽  
Han Fei ◽  
Jing Gao ◽  
Fang Fang Zhao
Keyword(s):  
Dynamic Recrystallization ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Reduction Method ◽  
Creep Mechanism ◽  
Creep Limit ◽  
Creep Properties ◽  
Second Phases ◽  
Thermal Extrusion

In this paper, the author successfully fabricated Mg-3Sr-xY alloys by melting-leaching reduction method using SF6 and N2 as protected gas. The microstructures of the Mg-3Sr-xY alloys were investigated in details，and the results showed that Mg-3Sr-xY alloys are composed of dendrite α-Mg and eutectic α-Mg and Mg17Sr2 and Mg24Y5 particulates, the second phases distribute in the α-Mg dendrites and interdendrites. The fiber microstructures form after thermal extrusion and the dynamic recrystallization occurs. In Mg-3Sr-xY alloy, the tensile strengths, the yield strengths and elongation rates increase firstly, reach the peak values, decrease with the increasing in Y content. Mg-3Sr-xY alloy have the best mechanics properties, including yield strengths and ultimate strengths and elongation rates and creep properties by the addition of 0.6%Y content. The tensile behaviors at elevated temperatures are accord to general laws for the metals at room temperature. The Mg-3Sr-xY alloys with 0.4-1.0% Y are of best creep limit. The dislocation sliding and climbing is the main creep mechanism for Mg-3Sr-0.6Y alloys.

Processing and Creep Performance of Silicon Carbide Whisker-Reinforced Silicon Nitride

1986 ◽  
Vol 78 ◽  
Author(s):  
John. R. Porter ◽  
F. F. Lange ◽  
A. H. Chokshi
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Silicon Nitride ◽  
Room Temperature ◽  
Full Density ◽  
X Ray Diffraction ◽  
Polycrystalline Alumina ◽  
Silicon Carbide Whisker ◽  
Transmission Electron ◽  
Composite Silicon

ABSTRACTSilicon carbide whisker reinforcement can significantly reduce creep rates in polycrystalline alumina [1], but the system SiC/Al2O3 is thermodynamically unstable in air and oxidizes to mullite during creep testing [2]. The system SiC/Si3N4 was investigated as a potentially more stable, high temperature structural composite. Silicon carbide whiskers were successfully incorporated into a silicon nitride matrix doped with alumina and yttria. Processing involved mixing dispersed slurries of silicon carbide and silicon nitride, adding the dopants as a solution of their nitrates and subsequently increasing the pH to precipitate the additive hydroxides. The resulting slurries were filter pressed at room temperature and hot pressed at 1650°C in graphite dies to full density. X-ray diffraction and transmission electron microscopy confirmed the presence of β-Si3N4, α-SiC and trace quantities of α-Si3N4, confirming that the α-β Si3N4 reaction occurred. An additional, as yet unidentified, minor phase was also detected.Whisker reinforcement was shown to increase the room temperature flexural strength and fracture toughness but high temperature creep performance was unaffected by whisker reinforcement.

Influence of High Temperature Processing on the Substructure of Laser Shock Processed Titanium Alloy

2014 ◽  
Vol 528 ◽  
pp. 44-53
Author(s):  
Yin Qun Hua ◽  
Yu Chuan Bai ◽  
Yun Xia Ye ◽  
Qing Xue ◽  
Hai Xia Liu ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Room Temperature ◽  
Laser Shock ◽  
Laser Shock Processing ◽  
Hardness Tester ◽  
Average Hardness ◽  
Transmission Electron ◽  
High Temperature Processing ◽  
Shock Processing

The paper aims to study the influence of high temperature processing on the substructure of laser shock processed titanium alloy. The titanium alloy specimens were first treated by laser shock processing (LSP), then treated at 700°C for three hours and air cooled to the room temperature to investigate the influence of the high temperature processing. To evaluate such influence, the hardness and substructure on the surface were investigated by micro hardness tester and transmission electron microscope (TEM), respectively. Results show that after three times LSP, the hardness of TC11 alloy was improved by 30.9%. The cause of such an improvement in hardness is that the crystal grains in the surface layer under the shock wave stress were strongly deformed, causing a dynamic recrystallization. The substructure is mainly twin crystals, highly tangled and dense dislocations. After high temperature processing in vacuum, the average hardness is decreased by 12% compared to that of the specimens after LSP. And the substructures are mainly small dislocation, nanocrystalline.

Direct Evidence of the Si Interstitialicy Injection and Fast diffusion effect in Si During Pulsed Laser Melt Process

1991 ◽  
Vol 230 ◽  
Author(s):  
Yih Chang ◽  
J. Chen ◽  
S. Talwar ◽  
E. Y. Shu ◽  
Thomas. W. Sigmon
Keyword(s):  
High Temperature ◽  
Temperature Gradient ◽  
Pulsed Laser ◽  
Fast Diffusion ◽  
Dislocation Loops ◽  
Diffusion Effect ◽  
High Temperature Gradient ◽  
Transmission Electron ◽  
Before And After ◽  
Dislocation Movement

AbstractHigh temperature gradient induced fast diffusion effect during pulsed laser melt processes is reported for the first time in the Si semiconductor. We use both the oxidationinduced stacking faults and dislocation loops as markers to determine the degree of enhanced diffusion in the unmelted Si substrate by tracing their movement after laser melt. The crosssectional transmission electron microscope is employed to investigate the defect structures before and after laser melt. The expanded dislocation loops exhibit a significant diffusion and climb occurring during the nanosecond-scale processing duration. We also formulate and solve the governed diffusion equation, based on a high temperature gradient induced electric field, to simulate the dislocation movement. The agreement between the experimental and simulated results verifies that the fast diffusion effect indeed occurs in the Si semiconductor during the pulsed laser melt period.

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