Search results

Cell blocks consist of a large number of dislocation cells (subgrains) and align in shear direction.
Fig. 2(a) shows the variation of the average subgrain and grain size against the number of passes determined by EBSD.
Fig. 2(b) shows the variation of the dislocation density against the number of passes.
The variation of (a) the average sugrain/grain size (b) the dislocation density (c) the fraction of HAGBs and (d) average misorientation angle for Cu, Ag, Cu-6.8Al, Cu-1Mn and Cu-5Ni processed by ECAP through different number of ECAP passes.
The fraction of the HAGBs is plotted in Fig. 2(c) as a function of the number of passes and comparable results for average misorientation angle is plotted in Fig. 2(d).

Keywords: gears, springs, grain coarsening, case-hardening, niobium, hardenability.
This level of strength has been the "new frontier" for a number of years.
C Si Mn P S Cr V 60SiCrV7 0.56-0.64 1.50-2.00 0.70-1.00 0.025 max 0.025 max 0.20-0.40 0.10-0.20 54SiCrV6 0.51-0.59 1.20-1.60 0.50-0.80 0.025 max 0.025 max 0.50-0.80 0.10-0.20 45SiCrV6 0.40-0.50 1.30-1.70 0.60-0.90 0.025 max 0.025 max 0.40-0.80 0.10-0.20 SAE 9260 0.56-0.64 1.80-2.20 0.75-1.00 0.035 max 0.040 max -- -- Grain size measurements performed according to the standard NF EN ISO 643 show that this small Nb addition is particularly effective in grain refinement (Fig.1). 5 7 9 11 13 800 850 900 950 1000 1050 Austenitizing temperature (°C) ASTM grain size number 60SiCrV7+Nb 60SiCrV7 SAE 9260 [13] Fig. 1.Austenite grain size versus austenitising temperature
This would lead to Nb segregation at the γγγγ grain boundaries and reduce the grain boundary energy available for transformation.
Austenite ASTM grain size index: 3/5 without Nb, 4/6 with 0.030 wt.% Nb.

Self-Diffusion Parameters of Grain Boundaries and Triple Junctions in Nanocrystalline Materials A.G.
Suggested methods describe the process of self-diffusion along grain boundaries and triple junctions in polycrystals without using geometric models of the grain boundaries structure.
Introduction Diffusion along grain boundaries (GB) in polycrystals is a process of atoms displacements with energy barriers overcoming in the grain boundary area, which forms the basis of the mechanisms of grain boundary migration, grain growth, the allocation of secondary phases at grain boundaries, Coble creep and other diffusion-controlled processes in polycrystals.
Significantly greater rate of diffusion along grain boundaries in comparison with the diffusion in the bulk of the crystal grains was found, the classification of regimes of grain boundary diffusion and grain boundary diffusion processes was studied in many polycrystals.
Following which effects on the model samples were switched off and the simulation was conducted by NVE (constant number of particles, volume and total energy) MD scheme.

When the boundary plane is exactly on {110} in the grain B, it is about 8° from {010} in the grain A.
Transmission topograph of migrating asymmetrical grain boundary Σ5 where the initial boundary plane is close to {010} in the left grain A and to {110} in the right grain B.
Only one grain was visualized in our experimental setting.
When the grain boundary curves and migrates it changes the plane orientation via the {110} plane in one grain and simultaneously via the {010} plane in the other grain.
Qualitatively much larger number of observations can be collected in comparison to classical heating/cooling cycles.

Anomalous Effect of Strain Rate on the Tensile Elongation of Coarse-grained Pure Iron with Grain Boundary Micro-voids Xin-Ming CAO1, Qi-Qiang DUAN3, Xiao-Wu LI1,2,a 1 Institute of Materials Physics and Chemistry, College of Sciences, P.O.
Experimental results Figure 1 shows the microstructures of the raw coarse-grained CP iron.
From Fig. 1(a), the average grain size was measured to be about 200 mm.
In addition, as representatively shown in a magnified SEM image of Fig. 1(b), a number of micro-voids were found to pre-exist at GBs, and most of the micro-voids are in the size of several microns.
Fig. 1 Initial microstructures of the raw coarse-grained CP iron.

Although their specific form is complex, it is not difficult to calculate their coarse-grained average.
Coarse-Grained Average of Field Variables Any macroscopic field variable and its corresponding microscopic or mesoscopic field variable can generally be related by coarse-grained averaging in space,
For example, the microscopic mass density field is , (9) where and are the mass and position of the k nucleus or electron respectively, and N is the total number of nuclei and electrons in the system.
It is obvious that the macroscopic mass density field ρ is equal to the coarse-grained average of .
Like velocity, displacement and strain are not coarse-grained averages.

Initial material was composed of grains ranging between 5 mm and 65 mm with large numbers of annealing twins, and its average grain size was 33 mm, as shown in Fig. 2(a).
As a result, CR processed material showed the significantly refined grains than that of initial material, in which grains ranged from 0.2 mm to 3 mm, with average grain size of 1.3 mm, as shown in Fig. 2(b).
At CRR processed material, the grains were more refined than that of CR, consequently, average grain size showed 0.6 mm, as shown in Fig. 2(c).
Further, at all cold rolled specimens, large numbers of annealing twins were distributed in microstructures, in common.
At all conditions, the high angle grain boundaries of the grain boundaries occupied more than 90% in fraction, as shown in Fig. 4.

There is a large number of methods for severe plastic deformation (SPD).
The grain size slightly differed between the samples, and different area dimensions and step sizes were chosen to maximize the number of data points and still get a good statistical results.
Fig. 3 (b) presents the grain boundary map of the same sample.
The commercial Al-1050 grain size is approximately 150μm [11].
EBSD results: (a) Texture and (b) Grain boundary maps (black: HAGB, green:LAGB); (c) grain size distribution and (d) grain boundary misorientation distribution of Al 1050 processed to 24 passes by CCDF.

Coarse-grained Parallel Genetic Algorithm To try to avoid the “precocity” and “deceit” phenomenon, we put forward a coarse-grained parallel genetic algorithm.
Use to express the path information from the -th node to the j-th node, and , (both “i” and “j” are integer values, and “n” is the number of network nodes).
Initial population. 1) First, find the connection between every node, and save the number of connected nodes into an array together with relevant path information. 2) Then initialize each individual as the zero individual, which means that the assembly information about the individual nodes are: (), =N.
（2） Fig. 2 The shortest path of the experiment simulation Conclusion The coarse-grained parallel genetic algorithm segments those randomly generated initial populations into several major sub-populations by the number of processors [5].
After the contrastive analysis of the calculation results of classic examples, we get some relevant conclusions on coarse-grained parallel genetic algorithm’s performance feature and optimal parameter setting.

The effect of the number of pressings on the tensile ductility is considerable.
The following conclusions can be drawn: (1) a rather equiaxed uniform grain/cell structure tends to form regardless of the processing route when the number of passes exceeds 16, although at smaller number of passes the grain shape depends on processing rather strongly [2,10]; the AR value in A specimens is even slightly higher than that in the Bc specimens indicating intensive fragmentation of the pan-cake or fibrous structure, which is typically formed after ECAP by route A during first pressings
It is apparent that the increasing number of pressings gives rise to considerable reduction of the total heat effect upon annealing.
Similarly, the facture surface appeared virtually independent of the number of passes.
We also notice some trend towards increasing ductility with increasing number of passes from 16 to 20.