Creep Deformation and Microstructure of Alloy 617 Foil at High Temperature

2007 ◽  
Vol 26-28 ◽  
pp. 233-236 ◽  
Author(s):  
S.K. Sharma ◽  
Jin Won Choi ◽  
K.J. Kang
Keyword(s):  
Grain Size ◽  
Steady State ◽  
High Temperature ◽  
Applied Stress ◽  
Creep Test ◽  
Steady State Creep ◽  
Maximum Elongation ◽  
Alloy 617 ◽  
Loading Direction ◽  
Average Grain Size

The present paper reports the results of microcreep tests and microstructure of alloy 617 foils of 100μm thick specimens at 800 and 900 oC in air. Before each test, the specimens were annealed in vacuum at 950 oC for 17 hrs. The dynamic recrystallizations were observed during creep test. The voids and cracks were observed along grain boundaries. The maximum elongation of grains was found at the lowest applied stress along the loading direction. The average grain size decreases from 20 μm to 2 μm as applied stress increases from 48 to 120 MPa at 800 oC and from 50 μm to 5 μm as the applied stress increases from 35 to 60MPa at 900 oC. The steady state creep rates were increased as applied stress increased in all the specimens.

Compressive creep of YBa2Cu3Ox

1990 ◽  
Vol 5 (12) ◽  
pp. 2766-2770 ◽  
Author(s):  
K. C. Goretta ◽  
J. L. Routbort ◽  
A. C. Biondo ◽  
Y. Gao ◽  
A. R. de Arellano-López ◽  
...  
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Steady State ◽  
Creep Rate ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Partial Pressures ◽  
Average Grain Size ◽  
Diffusional Flow ◽  
State Stress

YBa2Cu3Ox was deformed from 850 to 980 °C in oxygen partial pressures of 103 to 105 Pa. Steady-state creep rate, ̇, for P(O2) from 104 to 105 Pa could be expressed as ̇ = Aσ1.0 (GS)−2.8±0.6 exp −(970 ± 130 kJ/mole)/RT, where A is a constant, σ the steady-state stress, GS the average grain size, and R and T have their usual meanings, For P(O2) from 103 to 3 ⊠ 103 Pa, the activation energy decreased to about 650 kJ/mole and for a given temperature creep kinetics were much faster. The data and microscopic observations indicated that creep occurred by diffusional flow. Comparisons with diffusion data for YBa2Cu3Ox suggested that Y or Ba may be rate-controlling diffusing species.

scholarly journals Structural Transformations and Mechanical Properties of Metastable Austenitic Steel under High Temperature Thermomechanical Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 645
Author(s):  
Igor Litovchenko ◽  
Sergey Akkuzin ◽  
Nadezhda Polekhina ◽  
Kseniya Almaeva ◽  
Evgeny Moskvichev
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Temperature ◽  
Austenitic Steel ◽  
Structural Transformations ◽  
Initial State ◽  
Twin Boundaries ◽  
Metastable Austenitic Steel ◽  
Average Grain Size ◽  
Heating Up

The effect of high-temperature thermomechanical treatment on the structural transformations and mechanical properties of metastable austenitic steel of the AISI 321 type is investigated. The features of the grain and defect microstructure of steel were studied by scanning electron microscopy with electron back-scatter diffraction (SEM EBSD) and transmission electron microscopy (TEM). It is shown that in the initial state after solution treatment the average grain size is 18 μm. A high (≈50%) fraction of twin boundaries (annealing twins) was found. In the course of hot (with heating up to 1100 °C) plastic deformation by rolling to moderate strain (e = 1.6, where e is true strain) the grain structure undergoes fragmentation, which gives rise to grain refining (the average grain size is 8 μm). Partial recovery and recrystallization also occur. The fraction of low-angle misorientation boundaries increases up to ≈46%, and that of twin boundaries decreases to ≈25%, compared to the initial state. The yield strength after this treatment reaches up to 477 MPa with elongation-to-failure of 26%. The combination of plastic deformation with heating up to 1100 °C (e = 0.8) and subsequent deformation with heating up to 600 °C (e = 0.7) reduces the average grain size to 1.4 μm and forms submicrocrystalline fragments. The fraction of low-angle misorientation boundaries is ≈60%, and that of twin boundaries is ≈3%. The structural states formed after this treatment provide an increase in the strength properties of steel (yield strength reaches up to 677 MPa) with ductility values of 12%. The mechanisms of plastic deformation and strengthening of metastable austenitic steel under the above high-temperature thermomechanical treatments are discussed.

Study on Thermal Cycling of Sn0.7Cu Solder

2013 ◽  
Vol 791-793 ◽  
pp. 362-365
Author(s):  
Li Yang ◽  
Ju Li Li ◽  
Jing Guo Ge ◽  
Meng Li ◽  
Nan Ji
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
High Temperature ◽  
Thermal Cycling ◽  
Shear Strain ◽  
Maximum Shear Stress ◽  
Steady State Creep ◽  
Maximum Shear Strain ◽  
Cycle Number ◽  
State Cycle

Thermal cycling of a unit Sn0.7Cu solder was studied based on the steady-state creep constitutive equation and Matlab software. The results show that there is a steady-state cycle for the thermal cycling of unit Sn0.7Cu eutectic solder. In steady-state thermal cycling, the shear stress is increased with the increase of temperature. There is a stage of stress relaxation during high temperature. A liner relationship between maximum shear stress and maximum shear strain is observed during thermal cycling. The metastable cycle number is declined greatly with the increase of maximum shear strain.

scholarly journals Molecular Dynamics Simulation on Creep Behavior of Nanocrystalline TiAl Alloy

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1693
Author(s):  
Fei Zhao ◽  
Jie Zhang ◽  
Chenwei He ◽  
Yong Zhang ◽  
Xiaolei Gao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Grain Size ◽  
Steady State ◽  
High Temperature ◽  
Grain Boundary ◽  
Tial Alloy ◽  
Boundary Diffusion ◽  
Dislocation Motion ◽  
High Temperature Creep ◽  
Creep Stage

TiAl alloy represents a new class of light and heat-resistant materials. In this study, the effect of temperature, pressure, and grain size on the high-temperature creep properties of nanocrystalline TiAl alloy have been studied through the molecular dynamics method. Based on this, the deformation mechanism of the different creep stages, including crystal structure, dislocation, and diffusion, has been explored. It is observed that the high-temperature creep performance of nanocrystalline TiAl alloy is significantly affected by temperature and stress. The higher is the temperature and stress, the greater the TiAl alloy’s steady-state creep rate and the faster the rapid creep stage. Smaller grain size accelerates the creep process due to the large volume fraction of the grain boundary. In the steady-state deformation stage, two kinds of creep mechanisms are manly noted, i.e., dislocation motion and grain boundary diffusion. At the same temperature, the creep mechanism is dominated by the dislocation motion in a high-stress field, and the creep mechanism is dominated by the diffusion creep in the low-stress field. However, it is observed to be mainly controlled by the grain boundary diffusion and lattice diffusion in the rapid creep stage.

High-Temperature Steady-State Creep in Rutile

1963 ◽  
Vol 46 (9) ◽  
pp. 411-417 ◽  
Author(s):  
WALTER M. HIRTHE ◽  
JOHN O. BRlTTAIN
Keyword(s):  
Steady State ◽  
High Temperature ◽  
Steady State Creep

The Investigation of Creep Behavior for NiAl-28Cr-5.5Mo-0.5Hf-0.02wt.%P Alloy at High Temperature

2011 ◽  
Vol 279 ◽  
pp. 28-32
Author(s):  
Guang Ye Zhang ◽  
Dong Wen Ye ◽  
Jin Lin Wang ◽  
You Ming Chen ◽  
Long Fei Liu ◽  
...  
Keyword(s):  
Steady State ◽  
High Temperature ◽  
Creep Behavior ◽  
Fracture Behavior ◽  
Primary Creep ◽  
Dislocation Climb ◽  
Steady State Creep ◽  
Creep Fracture ◽  
Creep Mechanisms ◽  
Higher Temperature

The Microstructure and creep behavior for NiAl-28Cr-5.5Mo-0.5Hf-0.02wt.%P alloy at high temperature have been investigated in this paper. The results reveal that the high temperature creep behavior of the NiAl-28Cr-5.5Mo-0.5Hf-0.02wt.%P alloy is characterized by transient primary creep and dominant steady-state creep as well as ternary creep behavior. The primary creep can be described by Garofalo equation and the steady-state creep can be depicted by Dorn equation. The creep mechanisms are viscous glide of dislocations at lower and middle testing temperatures and dislocation climb at higher temperature. No change of the microstructure for the testing alloy indicates that the creep fracture is controlled by the formation and propagation of cavities and cracks, and the creep fracture behavior obeys Monk man-Grant relationship.

Effect of Deformation Route and Sc and Zr Addition on Ultra-Fine Grain Formation and Superplasticity in Al-Mg Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 847-852
Author(s):  
Suk Bong Kang ◽  
Jae Woon Kim ◽  
Hyoung Wook Kim
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Deformation Process ◽  
Mg Alloys ◽  
Fine Grained ◽  
Loading Direction ◽  
Zr Addition ◽  
Average Grain Size ◽  
Multiple Deformation ◽  
Al Mg Alloys

Recently the method for obtaining ultra-fine grained metallic materials has developed using severe plastic deformation (SPD), such as equal channel angular pressing (ECAP), accumulative roll bonding (ARB), torsion straining, and warm multiple deformation (WMD) etc. In order to enhance thermal stability of ultra-fine grained aluminum alloys manufactured by SPD process, the addition of Sc and Zr elements has been considered to devise fine Al3Sc, Al3Zr and Al3(Scx Zr1-x) precipitates for inhibiting the grain growth. In this study, the microstructure evolution has been investigated in Al-Mg alloys with and without Sc and Zr addition during the warm multiple deformation process. In addition Al-Mg alloys were compressed at a strain rate of 10-1 sec-1 by two different routes, that is, route A and route B. Route A is to rotate the specimen throughout 90o around the vertical axis of loading direction at every pass. Route B is to rotate the specimen throughout 90o around the parallel axis of loading direction and then rotate it again as route A. The specimen deformed by route B had finer grain size and more uniform distribution of grains than those deformed by route A. When the warm multiple deformation process repeated up to 8 passes at 673 K, the specimen consisted of ultra-fine grained structure with the average grain size less than 3 μm. The superplastic behavior can also be observed at the high strain rate and low temperature regime.

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