On the nature of the intergranular accommodation in the modeling of elastoviscoplastic behavior of polycrystalline aggregates

2021 ◽  
pp. 185-192
Author(s):  
A. Zaoui ◽  
J.L. Raphanel
Keyword(s):  
Polycrystalline Aggregates

scholarly journals First-principles generated mechanical property database for multi-component Al alloys: Focusing on Al-rich corner

2017 ◽  
Vol 53 (1) ◽  
pp. 1-7 ◽  
Author(s):  
J. Wang ◽  
Y. Du ◽  
X. Tao ◽  
Y. Ouyang ◽  
L. Zhang ◽  
...  
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Linear Thermal Expansion ◽  
Elastic Stiffness ◽  
Debye Model ◽  
Al Alloys ◽  
Processing Route ◽  
Temperature Dependent ◽  
Polycrystalline Aggregates ◽  
Strain Stress

Systematic first-principles calculations of the single crystal elastic stiffness constants (cij?s) and the polycrystalline aggregates including bulk modulus (B), shear modulus (G), Young?s modulus (E) have been performed for series binary and ternary Al compounds at 0 K. In addition, the temperature-dependent elastic properties for some technologically important phases are calculated. The cij?s are calculated by means of an efficient strain-stress method. Phonon density of states or Debye model is employed to calculate the linear thermal expansion, which is then used to calculate the temperature dependence of elastic properties. The calculated temperature-dependent elastic properties are compiled in the format of CALPHAD (CALculation of PHAse Diagram) type formula. The presently computed elastic properties for Al compounds are needed for simulation of microstructure evolution of commercial Al alloys during series of processing route.

Diffusion of potassium in single crystals and polycrystalline aggregates of molybdenum

1966 ◽  
Vol 8 (5) ◽  
pp. 412-414
Author(s):  
G. P. Benediktova ◽  
G. N. Dubinin ◽  
M. G. Karpman ◽  
G. V. Shcherbedinskii
Keyword(s):  
Single Crystals ◽  
Polycrystalline Aggregates

Computer Simulation of Grain Growth in Polycrystalline Aggregates

1982 ◽  
Vol 21 ◽  
Author(s):  
M. P. Anderson ◽  
D. J. Srolovitz ◽  
G. S. Grest ◽  
P. S. Sahni
Keyword(s):  
Grain Growth ◽  
Chemical Properties ◽  
Predictive Ability ◽  
Grain Morphology ◽  
Catalytic Efficiency ◽  
Second Phase ◽  
Controllable Factors ◽  
Polycrystalline Aggregates ◽  
Grain Growth Kinetics ◽  
Physical And Chemical

The physical and chemical properties of materials are determined in part by microstructure. Grain orientation and size in polycrystalline aggregates affect, for example, yield strength, catalytic efficiency, chemisorption, physisorption, fracture and a host of other properties. The final grain morphology is often determined by thermal processing, addition of a second phase, deformation, etc. However, in order to effectively tailor the microstructure for specific applications, the mechanism and kinetics of grain growth must be known. Unfortunately, present theories predict grain growth kinetics (1–3) which often differ from experimental observation, have little predictive ability with respect to microstructure and are not easily generalized to account for experimentally controllable factors.

scholarly journals The Glide Direction in Ice

1961 ◽  
Vol 3 (30) ◽  
pp. 1097-1106 ◽  
Author(s):  
W. Barclay Kamb
Keyword(s):  
Power Flow ◽  
Stress Component ◽  
Ice Crystal ◽  
Hexagonal Crystal ◽  
Plastic Properties ◽  
Axis Orientation ◽  
Cubic Metals ◽  
Non Linear ◽  
Polycrystalline Aggregates ◽  
Flow Law

AbstractThe failure to detect experimentally a glide direction in the ice crystal is satisfactorily explained by assuming that the crystal glides simultaneously in three symmetry-equivalent directions with a response to the shear stress component in each direction that is the same as that observed for the crystal as a whole or for polycrystalline aggregates—the typical non-linear, power-type flow law. A hexagonal crystal responding to stress by this type of “non-linear crystal viscosity” behaves very differently from a tetragonal one. For a tetragonal crystal, the glide directions are well defined in the response of the crystal if the power-flow-law exponent n exceeds n ~ 1·5, whereas for a hexagonal crystal a well-defined glide direction can be observed only if n > c. 5. The response of a hexagonal crystal is entirely independent of a-axis orientation if n = 3 exactly. For 3 < n < c. 5 the true glide direction should be weakly apparent, whereas for 1 < n < 3 the crystal should show a response weakly suggestive of preferred glide in a direction perpendicular to the true glide direction. In the observed range of n values for ice, 2 < n < 4, the expected response to simultaneous glide differs so slightly from the hitherto-postulated a-axis-independent, “non-crystallographic” glide as to be practically undetectable experimentally. This circumstance makes it possible to identify <>as the glide direction, from structural considerations alone, and to accommodate the plastic properties of the ice crystal into the modern concepts of crystal plasticity. It may be expected that hexagonal close packed and face-centred cubic metals at high temperatures, in steady state creep, will show translation gliding without well-defined glide directions.

scholarly journals The diffraction of electrons by single crystals

1931 ◽  
Vol 133 (821) ◽  
pp. 1-25 ◽  
Keyword(s):  
Single Crystals ◽  
Present Theory ◽  
Simple Theory ◽  
Complete Agreement ◽  
Surface Films ◽  
Wave Mechanics ◽  
Fast Electrons ◽  
Polycrystalline Aggregates ◽  
Slow Electrons ◽  
Cleavage Face

The Diffraction of Electrons by Single Crystals . 1. The diffraction of electron waves has been observed both with single crystals and with polycrystalline aggregates. So far most of the work with single crystals has been done with slow electrons of a few hundred volts energy. While the results are in general agreement with wave mechanics, they differ considerably from the predictions of the simple theory, even when the latter is extended to include a consideration of the inner potential of the crystal. Part of the discrepancy is caused by undue simplification of the theory, and better results have been got with the more elaborate theory of Morse, but there are a number of cases in which beams corresponding to half order spectra and reflection by “forbidden” crystal planes have been recorded, and for these the present theory is quite unable to account. Experiments with fast electrons on polycrystalline aggregates have shown results in full agreement with the simple theory, and it is hoped that electron diffraction will become a valuable method for the study of surface films Clearly, however, this cannot be done satisfactorily as long as there is any doubt of the ability of the existing theory to explain the diffraction by known structures. It is therefore of importance to see whether any abnormalities exist for single crystals with fast electrons. So far the only work in this connection is that of Kikuchi and others on mica, that of Niskikawa and Kikuchi on calcite, and some work by Emslie at Aberdeen on galena and calcite. Kikuchi’s work shows complete agreement with theory, but has unusual features on account of the large spacing of mica across the cleavage face. The work on calcite is complicated by charging up of the crystal, and galena, as the present author has found, changes under the influence of the rays, so that it is difficult to draw precise conclusions. No metals have been investigated. The present work has, therefore, been undertaken. It consists of a detailed investigation of the diffraction of electrons of from 30,000 to 50,000 volts by single crystals of rocksalt, copper and silver.

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