Deformation Mechanism Maps: Their Use in Predicting Creep Behavior

1976 ◽  
Vol 98 (2) ◽  
pp. 125-130 ◽  
Author(s):  
F. A. Mohamed ◽  
T. G. Langdon
Keyword(s):  
Steady State ◽  
Creep Behavior ◽  
Deformation Mechanism ◽  
Simple Form ◽  
Steady State Creep ◽  
Deformation Mechanisms ◽  
Total Strain ◽  
Improved Method

A simple form of deformation mechanism map is presented which graphically illustrates the behavior of materials under steady-state creep conditions. Examples are given of maps for deformation mechanisms occurring both independently and sequentially. The use of deformation mechanism maps in the prediction of creep behavior is reviewed in detail, and an improved method is presented for estimating the total strain experienced after long-term exposure to stress and temperature.

Steady-state creep behavior of hot isostatically pressed niobium carbide

1987 ◽  
Vol 22 (9) ◽  
pp. 1233-1240 ◽  
Author(s):  
R.D. Nixon ◽  
S. Chevacharoenkul ◽  
R.F. Davis
Keyword(s):  
Steady State ◽  
Creep Behavior ◽  
Niobium Carbide ◽  
Steady State Creep

A model of dislocation-controlled rheology for the mantle

1981 ◽  
Vol 299 (1449) ◽  
pp. 319-356 ◽  
Keyword(s):  
Steady State ◽  
Absorption Band ◽  
Laboratory Data ◽  
Tectonic Stress ◽  
Seismic Attenuation ◽  
Steady State Creep ◽  
Dominant Factor ◽  
Total Strength ◽  
Self Diffusion

The dislocation microstructure of mantle materials can account simultaneously for long-term steady-state creep, and for stress wave attenuation at seismic frequencies. The hypothesis that a single microstructural model explains therheology for characteristic times ranging from 1 to 1010 seconds can be used to restrict the class of permissible rheological models for the mantle. W e review steady-state dislocation dam ping models in order of increasing complexity, and reject those which do not satisfy laboratory data or geophysical constraints. This elimination procedure leads us to consider an organized microstructure, in which most dislocations are found inside subgrain walls. The cells contain relatively few dislocation links. These are free to bow under small, i.e. seismic, stresses. The time constant of this mechanism is controlled either by the diffusion of kinks or of point defects bound to the dislocation line. The glide of intragrain dislocations explains the m agnitude and frequency range of seismic attenuation. Steady-state creep is governed by recovery through climb and annihilation in cell walls. Under conditions of jog undersaturation, climb is controlled by jog formation in addition to self-diffusion, and the model requires a higher creep activation energy than for self-diffusion, in agreement w th observations on olivine. Quantitative agreement with laboratory data is achieved if the density of cell-wall dislocations is one to two orders of magnitude higher than the density of intracell dislocations. Self-diffusion is probably controlled by silicon diffusion at low pressure and by oxygen diffusion at high pressure. T he long-term tectonic stress is the dominant factor determining scale lengths; as a result, the total strength of the relaxation associated with bowing of intracell dislocation links is fixed by the geometry and is of the order of 10 % . This limits the width of the seismic absorption band to 2 -3 decades in frequency for each mantle mineral. T he actual position of the seismic absorption band is determined primarily as a result of a trade-off between temperature, pressure and tectonic stress. This model provides a physical framework within which the quality factor and viscosity are related via the dislocation microstructure.

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.

Improved tensile creep properties of yttrium- and lanthanum-doped alumina: a solid solution effect

2001 ◽  
Vol 16 (2) ◽  
pp. 425-429 ◽  
Author(s):  
Junghyun Cho ◽  
Chong Min Wang ◽  
Helen M. Chan ◽  
J. M. Rickman ◽  
Martin P. Harmer
Keyword(s):  
Solid Solution ◽  
Steady State ◽  
Creep Behavior ◽  
Solubility Limit ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Creep Properties ◽  
Uniform Microstructure ◽  
Equiaxed Grains ◽  
Rare Earth Doped

The tensile creep behavior of yttrium- and lanthanum-doped alumina (at dopant levels below the solubility limit) was examined. Both compositions (100 ppm yttrium, 100 ppm lanthanum) exhibited a uniform microstructure consisting of fine, equiaxed grains. The creep resistance of both doped aluminas was enhanced, compared with undoped alumina, by about two orders of magnitude, which was almost the same degree of improvement as for materials with higher dopant levels (in excess of the solubility limit). In addition, measured creep rupture curves exhibited predominantly steady-state creep behavior. Our results, therefore, verified that the creep improvement in these rare-earth doped aluminas was primarily a solid-solution effect.

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