Alternative Length Scales for Polycrystalline Materials

1990 ◽  
Vol 209 ◽  
Author(s):  
C.S. Nichols ◽  
R.F. Cook ◽  
D.R. Clarke ◽  
D.A. Smith
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Cluster Size ◽  
Constitutive Relations ◽  
Physical And Mechanical Properties ◽  
Polycrystalline Materials ◽  
Length Scale ◽  
Average Cluster Size ◽  
Average Cluster ◽  
Relevant Length Scale

AbstractIt is well established from studies of bicrystals that the properties of a grain boundary depend on the atomic structure of the boundary. However, constitutive relations for the properties of polycrystalline materials do not currently take into account this boundary-toboundary variability. Instead, such relations depend on a single length scale, typically the average grain diameter. We extend the traditional viewpoint by proposing that boundaries may be divided into two distinct categories, depending on their misorientation angle. The relevant length scale in constitutive relations for polycrystals is then the average cluster size, where clusters consist of grains connected by boundaries in the same misorientation category. A brief discussion of this additional length scale and how it may be reflected in various constitutive relations for physical and mechanical properties of polycrystals is given.

Structure and properties of compact articles from high-alloyed iron powder with adding of boron nitride

2020 ◽  
pp. 39-48
Author(s):  
B. O. Bolshakov ◽  
◽  
R. F. Galiakbarov ◽  
A. M. Smyslov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Grain Boundary ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Operating Conditions ◽  
Structure And Properties ◽  
Steam Turbines ◽  
Friction Forces ◽  
Wide Range

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

Clustering in some randomly occupied two- and three-dimensional lattices

2004 ◽  
Vol 82 (4) ◽  
pp. 323-329
Author(s):  
A Ulug ◽  
M Karakaplan ◽  
B Ulug
Keyword(s):  
Percolation Threshold ◽  
Coordination Number ◽  
Cluster Size ◽  
Three Dimensional ◽  
Occupation Probability ◽  
Average Cluster Size ◽  
Number Of Clusters ◽  
Size Dimension ◽  
Average Cluster

Clustering in some two- and three-dimensional lattices is investigated using an algorithm similar to that of Hoshen–Kopelman. The total number of clusters reveals a maximum at an occupation probability, pmax, where the average cluster size, 2.03 ± 0.07, is found to be independent of the size, dimension, coordination number, and the type of lattice. We discussed the fact that the clustering effectively begins at pmax. The percolation threshold, pc, and pmax are found to get closer to each other as the coordination number increases. PACS Nos.: 64.60.Ht, 64.60.Qb, 82.30.Nr

Deformation of a [001] Σ13 grain boundary in silicon

1992 ◽  
Vol 50 (1) ◽  
pp. 250-251
Author(s):  
Laurent Sagalowicz ◽  
William A. T. Clark
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Crystal Lattice ◽  
Grain Boundaries ◽  
Important Influence ◽  
Polycrystalline Materials ◽  
Symmetrical Loading

The interaction between crystal lattice dislocations and grain boundaries has an important influence on the mechanical properties of polycrystalline materials. We describe here a study of the behavior of the Σ13, (510)1, 22.67°/[001] grain boundary in Si, deformed under symmetrical loading. The dissociation of crystal lattice dislocations which interact with this boundary during deformation is far more complicated than simple geometrical models predict.

scholarly journals Phase segregation in a system of active dumbbells

2014 ◽  
Vol 25 (12) ◽  
pp. 1441004 ◽  
Author(s):  
Giuseppe Gonnella ◽  
Antonio Lamura ◽  
Antonio Suma
Keyword(s):  
Low Temperatures ◽  
Cluster Size ◽  
Cluster Formation ◽  
Phase Segregation ◽  
Average Cluster Size ◽  
Dense Phase ◽  
Kinetics Of ◽  
Average Cluster ◽  
System Phase

A systems of self-propelled dumbbells interacting by a Weeks–Chandler–Anderson potential is considered. At sufficiently low temperatures the system phase separates into a dense phase and a gas-like phase. The kinetics of the cluster formation and the growth law for the average cluster size are analyzed.

Modeling of the Plastic Deformation of Polycrystalline Materials in Micro and Nano Level Using Finite Element Method

2013 ◽  
Vol 22 ◽  
pp. 41-60 ◽  
Author(s):  
Mohammad Jafari ◽  
Saeed Ziaei-Rad ◽  
Nima Nouri
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Finite Element ◽  
Dislocation Density ◽  
Grain Boundary ◽  
Constitutive Equations ◽  
Nanocrystalline Materials ◽  
Boundary Phase ◽  
Polycrystalline Materials ◽  
Microcrystalline Materials

Recent experiments on polycrystalline materials show that nanocrystalline materials have a strong dependency to the strain rate and grain size in contrast to the microcrystalline materials. In this study, mechanical properties of polycrystalline materials in micro and nanolevel were studied and a unified notation for them was presented. To completely understand the rate-dependent stress-strain behavior and size-dependency of polycrystalline materials, a dislocation density based model was presented that can predict the experimentally observed stress-strain relations for these materials. In nanocrystalline materials, crystalline and grain-boundary were considered as two separate phases. The mechanical properties of the crystalline phase were modeled using viscoplastic constitutive equations, which take dislocation density evolution and diffusion creep into account, while an elasto-viscoplastic model based on diffusion mechanism was used for the grain boundary phase. For microcrystalline materials, the surface-to-volume ratio of the grain boundaries is low enough to ignore its contribution to the plastic deformation. Therefore, the grain boundary phase was not considered in microcrystalline materials and the mechanical properties of the crystalline phase were modeled using an appropriate dislocation density based constitutive equation. Finally, the constitutive equations for polycrystalline materials were implemented into a finite-element code and the results obtained from the proposed constitutive equations were compared with the experimental data for polycrystalline copper and good agreement was observed.

A Comparative Study of Dose Loss and Diffusion for B11 and BF2 Implants

2000 ◽  
Vol 610 ◽  
Author(s):  
Reza Kasnavi ◽  
Peter B. Griffin ◽  
James D. Plummer
Keyword(s):  
Comparative Study ◽  
Cluster Size ◽  
The Other ◽  
High Dose ◽  
Interface Traps ◽  
Average Cluster Size ◽  
Pile Up ◽  
And Diffusion ◽  
Average Cluster ◽  
Simple Average

AbstractWe have studied dose loss for B11 and BF2 implants with energies ranging from 10 keV to 1keV for B11 and 45 keV to 2keV for BF2. We found that B11 implants during a 1050C-10s RTA anneal segregate mainly to the bulk of the oxide. High dose BF2 implants on the other hand, show significantly larger amounts of dose loss after stripping the oxide, due to a pile-up of boron at the Si/SiO2 interface. In order to simulate B11 diffusion we have introduced a simple average cluster size model to simulate Boron-Interstitial-Cluster (BIC) evolution. For BF2 implants, we have simulated the effect of F by reducing the damage and we have used interface traps to account for the dose loss observed experimentally. Using these models, we have been able to fit the SIMS profiles across the whole matrix of implant conditions for both B11 and BF2 implants.

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