Search results

Grain sliding or other types of grain boundary accommodation mechanisms are thought to predominate in this regime.
The differences in the grain growth observed can therefore be attributed to differences in grain boundary mobility.
Grain boundary sliding, or motion of the grains relative to each other in a direction parallel to the grain boundary does not require mass transport to maintain the preferred equilibrium partition of the impurities between grain boundary and bulk.
On the other hand, grain boundary migration and grain growth imply motion of the grain boundaries perpendicular to the grain boundary plane and require mass transport of the impurity together with GB motion in order to maintain the equilibrium segregation ratio.
Our technique will allow the engineering of interfaces for desired grain boundary mobility and mechanical response, something that is crucial for a number of applications such as building better targets for the National Ignition Facility which Figure 9: Results of the shock wave simulation in pure and micro alloyed samples (a) as prepared) (b) pure Cu sample (c) Sample containing 3% Fe.

After hot-band annealing at 850°C for 1h, grains coarsened dramatically.
It can make grains coarse and uniform in hot rolled strips, reduce the number of grain boundaries, aggregate and coarsen precipitates.
And it decreases (111) grains which nucleate along grain boundaries easily, while increases (100) and (110) grains, thus improves magnetic properties of electrical steel[1,2].
It's obvious that deformed grains in hot-rolled bands have recrystallized completely and the grain size of normalized samples is bigger than that of untreated ones.
Hence, grains coarse obviously.

For the coil inner part, the strengthening effects were made of fine-grained strengthening and M/A islands strengthening.
The number of M/A island in outer part is less than that in inner part, but much than that in middle part.
The blocky ferrite number in middle part increases significantly and grain sizes become larger.
The microstructure is finer, fine-grained strengthening effect is more obvious [1].
Subgrain size is smaller and the number is more, its strengthening effect is more apparent [1].

Therefore, different authors have concentrated on determining the active number of cutting edges.
(9) Hence, the total number of grains Ng,tot on the side surface of the core drill (da = outer diameter, di = inner diameter of the drill) can be calculated: (10) Two grain distributions are assumed.
Trajectories in phase (Figure 9) occur when the length of an ultrasonic vibration in tangential direction exactly corresponds to a whole-number multiple of the tangential grain distance.
Since the results change with the radius due to the different number of grains on each radius, calculations need to be conducted for each radius and averaged.
The material removals have to be multiplicated with the US-frequency and the number of grains on the front surface of the tool to obtain a microscopic material removal rate MRRmi (Eq. 13).

(3) where is the local free energy density, p is the number of lro parameters considered in a particular simulation, and ki and kc are the gradient coefficients which determine the width and the energy of the surface and grain boundary regions for a given f0 [15].
For simplicity, the diffusion coefficients have been assumed to be the same value within grains, e.g. , and grain boundaries in these simulations. p=36, according to Chen and Wang [17], such a number provides a reasonably good description of a polycrystalline microstructure.
Finally, in the region of these circles, the following values were assigned to the parameters: ,, i is a randomly natural number between 1 and 36, and c=1.
Then pore appears as black spots, grains are bright and grain boundaries gray.
Depending on the initial coordination number of the surrounding particles, the pores may have different shapes, as shown in Fig. 3(a) and (f).

Larger tensile thermal strains develop when the (0001) pole of adjacent grains lies closer to the grain boundary normal.
This is a complex problem, and there have been a number of different 2D and 3D approximations (e.g. [2], [3]), using abstract representations of the microstructure.
The numbers of identifiable crystallographic orientations, grains and grain boundaries were 886, 1047 and 5725 respectively (isolated regions of the same orientation were treated as separate grains).
a) b)c)d) Figure 4: The variation of average stress normal to grain boundaries as a function of a) relative misorientation between the (0001) poles in the adjacent grains, b) grain boundary area c) boundaries within a range of misorientation of the (0001) pole and the grain boundary pole for both grains, and d) boundaries within a range of misorientation of the (0001) pole and the grain boundary pole for one or both grains.
The cumulative numbers of grain boundary facets in each range of misorientation or size are also shown.

As shown in Fig.3 (a), a large number of deformed austenite microstructure and a small amount of recrystal grains with size of 5~10mm were observed when the strain rate was 1s-1.
In the case that the strain rate was 0.1s-1 as shown in Fig.3 (b), the number and size of the recrystal grains increased compared with that obtained at the strain rate of 1 s-1.
When the strain rate was 0.05 s-1, the uniform grains with size of approximately 20mm as well as a small number of deformed grains were observed as shown in Fig.3 (c).
As shown in Fig.4 (a), a large number of deformed austenitic grains and a small amount of recrystal grains were observed when the deformation temperature was 900℃.
In the case that he deformation temperature was 950℃ as shown in Fig.4 (b), the number of fine recrystal grains increased obviously.

And when Gd content increases to 1.2wt.% and 1.5wt.%, the number of precipitates increase and they distribute along grain boundaries as discontinuous net microstructure, as shown in Fig.2(d-e).
As shown in Fig.1(a), the grains in Zn-25Al-5Mg-2.5Si alloy are coarse and adding 0.4wt%- 1.2wt% Gd, the grains become smaller(Fig.1c-e).
According to this relationship, the smaller the grain size, the higher the strength.
So the tensile strength of alloy with the smallest grain size should be the highest when Gd content is 0.8wt.%.
When Gd content is 0.8wt.%, the optimized grains refining effect on the alloys is obtained

Optimization of Ultra-fine Limestone Filler on Cement Grain Composition Wen Xua, Fei Guob and Qian Tianc State Key Laboratory of High Performance Civil Engineering Materials, Jiangsu Research Institute of Building Science, Jiangsu Bote New Materials Co., Ltd., Nanjing 210008, China axuwen@cnjsjk.cn, bguofei@cnjsjk.cn, ctianqian@cnjsjk.cn Keywords: limestone filler; grain composition; rheology; Andreasen model; cement.
An experimental investigation was carried out to evaluate the effect of limestone filler (LF) with equivalent replacement of cement on its grain composition.
Reasons for the above were discussed in this paper from the point of the perfect effect of LF on the cement grain composition.
(2) Where D is the least square error, i is some particle size distribution point, n is the number of particle size distribution points, mi is the cumulative percentage under sieve at particle size distribution point i and Mi is the cumulative percentage under sieve at particle size distribution point i when the particle system is ideal.
Table 2 Particle size distributions of different powder materials and their least square errors to reference particle size distribution (μm) <0.50 <1.50 <3.10 <6.00 <12.5 <25.0 <51.0 <73.0 <103 (%) C 0 4.37 9.40 19.54 40.99 69.25 90.29 95.79 98.69 0.831 LP1 3.25 14.19 28.45 46.14 64.39 75.09 85.99 93.69 99.02 / LP2 3.28 25.67 50.62 74.06 93.75 99.20 99.90 100 100 / LP3 3.88 40.68 60.84 82.71 99.15 100 100 100 100 / C+LP1 0.65 6.33 13.21 24.86 45.67 70.42 89.43 94.97 98.76 0.560 C+LP2 0.66 8.63 17.64 30.44 51.54 75.24 92.21 96.23 98.95 0.475 C+LP3 0.78 11.63 19.69 32.17 52.62 75.40 92.23 96.23 98.95 0.430 Mi (%) C 14.94 21.54 27.44 34.20 43.68 55.03 69.80 78.66 88.22 0 The situation of the grain composition of powder materials can be reflected by the least square error D and more differences are shown between the actual particle systems and the ideal one with larger D.

The reason of this the dislocation density is bigger near by the grain boundary than inside the grains.
The number of grains, the diameter of the grains, and the boundary interface were measured by the image analyzer software.
Where is eutectic along the grain boundary there are much more new grain.
In order to distinguish the non-deformed original grains from the DRX grains, the recrystallized grains are defined as grains having an average diameter of <50 μm and the volume fraction of fine grains Vf is defined as follows [6]: Vf=Total area of individual fine grains AfTotal sampling area Ai Fig. 11.
The nucleation and grain grow of recrystallized grains occur along the eutectic phase.