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Annealing for 5 min resulted into full recrystallization, whereas at 10 min abnormal grain growth emanated from the mid section.
At 1 hr, the grains at the mid section and inner core (~300µm) were excessively larger than the outer surface (~20µm).
Unlike recrystallization which is driven by stored strain energy, normal and abnormal grain growth are controlled by grain boundary energy and mobility.
This imply that during prolonged annealing the neighboring <111> grains, having higher mobility, will grow faster than neighboring <100> grains, resulting in larger <111> grains, which in turn will grow at the expense of <100> grains because of their size advantage.
Acknowledgement The financial support given by the National Science Foundation (NSF) through the PREM program, grant number DMR 0351770 is gratefully acknowledged.

After pre-dressing, the protrudent grains grind the workpiece, the grains and the passivating film wear down.
Other experiment conditions are Grinding wheel: cast iron bond diamond wheel 120 #,¶200×10×5; resin bond diamond wheel 120 #, ¶200×10×5(grain size 125~106 micron); cast iron bond diamond wheel 240 #, ¶200×10×5(grain size 75~53 micron).
By reducing the grain size in a grinding layer, the number of grains increases by the square of the grain size reduction.
The big enhancement of the higher number of active grains means a reduction of the mechanical treatment by each single grain, because the same material is removed by a higher number of active grains.
The question is that the conventional use of fine grain wheels can generate very high grinding forces and unstable processes.

On the left hand size: ultra-coarse alloy with WC mean grain size of 4.8 µm and on the right hand size: medium-grained alloy with WC mean grain size of 2 µm [12].
A number of coarse-grain carbide samples with different carbon contents, the microstructures of which are shown in Fig. 33, were made and WC/WC grain boundaries were examined with respect to their contact angles with the Co-based binder, which is schematically shown in Fig. 34 and Fig. 35. 10 µm a 10 µm b Figure 33.
A number of samples sintered in different furnaces and in various sintering processes were examined.
To answer this question we analysed the surface of a great number of carbide articles from different grades varying in both the Co content and WC mean grain size after their sintering in large industrial sinter-HIP furnaces.
When the WC grain size of cemented carbides with 10%Co is increased the Co content on the surface after sintering noticeably decreases, so that the surface of the medium-grained grade with WC mean grain size of about 1.5 µm usually contains below 20 wt.% Co In this case cobalt forms a limited number of islands covering WC grains on the carbide surface and never a continuous film, which is shown in Fig.42b.

Precipitates of  hypereutectoid cementite in the WMT roll occurred along grain boundaries of primary austenite.
A large fraction of spheroidal hypereutectoid cementite, precipitated in the whole volume of the primary austenite grain, appeared in the WNT roll.
Precipitates of hypereutectoid cementite in the WMT roll occurred along grain boundaries of primary austenite (see Fig. 1c).
A large fraction of spheroidal hypereutectoid cementite, precipitated in the whole volume of the primary austenite grain, appeared in the WNT roll (Fig. 1b).
Mazur, The influence of grain size upon the fracture toughness of the hot-work tool steel, Scandinavian Journal of Metallurgy 12/1 (1983) 22-28

This quantity is the number of jump attempts per particle during the calculation.
In Fig. 1 the effective diffusivity as calculated by LMC is shown as a function of grain boundary fraction g for a cubic grain model[12].
Other grain models have also been analyzed with LMC and have shown transition points at Λ = 0.4 for the square grains model and Λ = 1.5 for the cubic grains model[18].
Np is the number of particles which is linearly related to the oxygen concentration.
For the common situation where the surface temperature is held constant at T0, the number of virtual thermal particles at the source is held at �n.

By annealing, the nanocrystalline layers showed substantially slow grain growth without recrystallization.
The experiments done at room temperature under the same condition required a larger number of impacts than at LN2 temperature to form NC regions.
The DF image shows that the ferrite grain size is less than 20 nm, and the SAD pattern indicates that the ferrite grains are randomly oriented.
If the hardness of 3.8 GPa is due to grain boundary strengthening, the grain size is estimated to be 290 nm according to the Hall-Petch relationship for iron (HV [GPa] = 0.36 + 59d -1/2 [d: nm]).
By annealing, NC layers showed substantially slow grain growth without recrystallization.

Introduction It is now well established that processing through the application of severe plastic deformation (SPD), typically, equal channel angular pressing (ECAP) is especially effective in grain refinement and product ultra fine grained materials (grain size in the range of 100-400nm) which lead to increase of strength and toughness, simultaneously [1, 2, 3].
founded that with increasing the number of ECAP passes in AISI 304L stainless steel the tensile strength and hardness increase, however, the elongation and strength hardening rate decrease [8].
Although grains parallel with Y direction sheared and made angles 20˚ up to 80˚ with Y axis.
In Y plane, grains were elongated on the angle of about 25-30˚ with respect of X direction.
Influence of Vickers hardness on the number of ECAP passes.

The main process parameters responsible for the final properties are slab reheating temperature, number of deformation passes, reduction per pass, start and finish rolling temperatures in roughing, but specially in finishing rolling, delay or holding time between rough and finish stages, cooling rate together with stop cooling temperature and coiling temperature.
Already in 1924 Arrowsmith [3] reported the advantages of grain refinement.
The grain definition criterion was considered as 15° and min. 5 point /grain.
The cumulative grain size distribution curves (equivalent diameter) are shown in Fig. 6.
The mean grain sizes in equivalent grain diameter which are given in Fig. 6 showed that the low SFRT gives rise to the fine grained microstructure which is not significantly dependant on the cooling rate.

The average bead diameter was 51 μm and contained 0.3 μm grains.
More recently a large number of studies have sought to develop nano-scale microstructures.
Grain size was measured on the surface of the particles which was sufficiently thermally etched to see grain boundaries.
In this case we have fit to several different Al2O3 grain sizes not knowing the exact grain size.
Acknowledgement Financial support for this work came from Basic Energy Sciences Division of the Department of Energy Grant Number DE-FG02-O2ER46010.

In the second part of this paper, we extract Leff from literature data of polycrystalline silicon cells, with grain sizes from 10-2 to 10 4 µm, modeling the extracted Leff as a function of the grain size g, and the recombination velocity SGB at the grain boundaries.
The efficiency of a solar cell generally increases with increasing grain size g [1].
The explanation for this increase is simple: if g increases, the ratio of grain boundary area to grain volume decreases, reducing the amount of recombination centers, increasing the minority carrier diffusion length.
A large number of the columnar grains must therefore be separated by [110] tilt grain boundaries.
The increase of diffusion length with grain size is then modeled with an equation that considers the recombination velocity at the grain boundaries.