On the activation energy for high temperature steady state creep

1961 ◽  
Vol 9 (11) ◽  
pp. 1035-1036 ◽  
Author(s):  
R.G. Davies
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
High Temperature ◽  
Steady State Creep

High Temperature Strength and Stability of Oxide Dispersion Hardened Alloys

1975 ◽  
Vol 33 ◽  
pp. 174-175
Author(s):  
M.S. Grewal ◽  
S.A. Sastri ◽  
N.J. Grant
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
High Temperature ◽  
High Stability ◽  
High Strength ◽  
Steady State Creep ◽  
High Temperature Strength ◽  
Oxide Dispersion ◽  
Steady State Creep Rate ◽  
Image Position

The creep behavior of oxide dispersed alloys can be described by the following equation:where ε is steady state creep rate, σ applied stress, R gas constant, T temperature in °K, Qc activation energy for creep, n stress exponent, A and n are constants.Two unusual observations in the case of O.D. alloys are that Qc and n take on values that have not been explained satisfactorily. This investigation was undertaken to explain the unusually high strength, high Qc and high stability (high value of n) in the oxide dispersed alloys.

High-Temperature Creep of Nb-Al-V Alloys

1998 ◽  
Vol 552 ◽  
Author(s):  
Tie-Sheng Rong ◽  
Mark Aindow
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
High Temperature ◽  
Creep Deformation ◽  
Steady State Creep ◽  
High Temperature Creep ◽  
Creep Mechanisms ◽  
Creep Curves ◽  
Rapid Transition ◽  
A15 Phase

ABSTRACTNb-15A1-20V alloys with about 45% by volume of an A15 phase in a B2 matrix have been subjected to creep deformation at temperatures between 1000°C and 1200°C and stresses from 80 MPa to 240 MPa in vacuum. The creep curves show a rapid transition from primary to steady-state creep with a well-defined activation energy. Microstructural observations show that the creep deformation occurs mainly in the B2 matrix and is controlled by dislocation mechanisms. Samples which had been coldrolled and annealed to reduce the size of A 15 precipitates and increase the yield strength were found to have lower creep resistance than those with unrefined microstructures. The significance of these observations for the creep mechanisms is discussed.

Microstructure and Creep Property of DZ125 Nickel-Based Superalloy

2013 ◽  
Vol 747-748 ◽  
pp. 697-702 ◽  
Author(s):  
Su Gui Tian ◽  
Xian Lin Meng ◽  
Ning Tian ◽  
Hui Chen Yu
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
High Temperature ◽  
Deformation Mechanism ◽  
Creep Property ◽  
Steady State Creep ◽  
Nickel Based Superalloy ◽  
Microstructure Observation ◽  
Initiation And Propagation ◽  
Property Measurement

By means of creep property measurement and microstructure observation, an investigation has been made into the creep behaviors of DZ125 superalloy at high temperature and low stress. Results showed that the superalloy under the applied stress of 137MPa at 1293 K displayed a better creep resistance, and the apparent creep activation energy of the alloy during steady state creep was measured to be Q = 325.57 kJ/mol. The various microstructures were displayed in different regions of the sample, thereinto, the rafted γ phase was uniformly distributed in the regions far away from the fracture, but the twisted and coarser rafted γ phase appeared in the region near the fracture. The deformation mechanism of the alloy during steady state creep was the dislocations climbing over the rafted γ phase. In the later stage of creep, significant amount of dislocations shearing into the rafted γ-phase promoted the initiation and propagation of the cracks along the boundaries up to the occurrence of fracture, which was though to the fracture mechanism of the alloy during creep.

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.

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.

Compressive creep of dense Bi2Sr1.7CaCu2Ox

1992 ◽  
Vol 7 (9) ◽  
pp. 2360-2364 ◽  
Author(s):  
J.L. Routbort ◽  
K.C. Goretta ◽  
D.J. Miller ◽  
D.B. Kazelas ◽  
C. Clauss ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Activation Energy ◽  
Transmission Electron Microscopy ◽  
Steady State ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Lower Stress ◽  
Dislocation Glide ◽  
Transmission Electron ◽  
Partial Pressures

Dense polycrystalline Bi2Sr1.7CaCu2Ox (2212) was deformed from 780–835 °C in oxygen partial pressures, Po2, of 103 to 2 × 104 Pa. Results could be divided into two stress regimes: one at lower stress in which the steady-state creep rate, ∊, was proportional to stress, γ, having an activation energy of 990 ± 190 kJ/mole and being independent of PO2, and another at higher stress in which ∊ was proportional to σn, with n ≍ 5–6. Transmission electron microscopy supported the interpretation that in the lower-stress viscous regime, creep was controlled by diffusion, whereas dislocation glide and microcracking were responsible for strain accommodation at higher stresses.

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