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However, their applicability is hindered due to the poor workability owing to the hexagonal close-packed (HCP) crystal structure and consequent limitations on the number of available slip systems [1].
Microstructure of the ZM21 alloy reveals single phase with an average grain size ~ 400µm and AZ91 alloy shows α-Mg and continuous b (Mg17Al12) precipitates along the grain boundary.
The recrystallized grain size is in the range 20-30µm.
However, the presence of β-phase in AZ91 may facilitate grain refinement by inducing large strain adjacent to the grain boundary and inhibit the growth of recrystallized grains.
At high temperatures, as in the present case, bulging of existing grain boundaries controlled by dislocation climb results in the formation of new DRX grains.

It is clear that a number of large recrystallized grains have formed but that there is a gradation in grain size: this being finer nearer the compression surface.
On the side of the recrystallized band towards the neutral axis, grains reached more than 200 µm in size, indicating fewer grains but more growth.
Most grain boundary misorientations lay below 10° although an increasing number lay in the range 10° to 20°.
Accompanying this, a large number of high angle grain boundaries (30°- 45°) were found, suggesting that a few fine-scale recrystallized grains may have been nucleated.
And grain boundary misorientation in recrystallized areas of compressed regions increased with increase in the recrystallized grain size.

With an increase of ECAP number up to 3, a great number of parallel shear bands can be observed, while, grains are inclined at an angle of 90º to transverse direction (Fig. 7c).
This is because repeated deformation increases the number and misorientation of the boundaries of deformation bands.
Many researchers [18] [46] mentioned that, by increasing the number of passes, the dislocation density inside the sub-grains becomes saturated and then a significant reduction is observed inside the cells.
It can be observed that the hardness varies with the number of passes in a manner expected for large strain deformation.
The obtained microstructures are refined by the interaction of shear bands and their increase in number.

Introduction Because of many factors troubled food security are still exist, there are still a number of global population faces food crisis.
Total grain output.
In the technology conditions remain unchanged, under the prerequisite of one country resources means that the country the reduction of the number of total grain output and supply drop; And a decrease in the level of agricultural production technology means that the same input can only get fewer food production.
Import rate of the grain.
Grain output volatility.

Fatigue Behavior of Age-Hardening Cu-6Ni-1.5Si Alloys with Different Grain Sizes M.
Fig. 3 shows Vickers indentation pressed inside a grain (load = 0.49 N).
The number of cycles to initiate a grain-size crack (l ⁓ 0.04 mm) in the NR specimen is about 3 times larger in that in the CR specimen (l ⁓ 0.1 mm).
This is because that the grain size of CR specimen was larger than the NR specimen.
Cold-rolling before SHT brought a grain growth during a heating at SHT.

All these techniques resulted in pronounced grain refinement.
Currently, austenitic stainless steels are widely used for a number of structural applications [3].
This microstructure is composed of alternating nano-scale austenite and matrensite grains.
Only austenitic nano-scale grains with an average size of ~23 nm evolve during HPT (Fig. 1c).
Langdon, Twenty-five years of ultrafine-grained materials: Achieving exceptional properties through grain refinement.

The results are then passed up to a grain-level simulation where the response of a statistically significant particle ensemble is simulated via the evolution of particle distributions.
The growth of embrittling phases, particularly on the grain boundary, can also reduce the ductility of the material.
The instantaneous state of a material microstructure is assumed to be characterized by the mean grain size, the mean dislocation density and the number, size, location and composition of the different precipitate phases.
In this paper we restrict our consideration to the evolution of the precipitate phases, as little change in the grain size in IN617 is observed (due to the generous coating of carbides along the grain boundaries).
The subsequent decrease in particle number is due to coarsening.

It was established that upon SPD a number and a size of aluminides decrease with increasing a degree of deformation.
The number of anvil revolutions was varied from 0.5 to 10 (equivalent to logarithmic true train e = 3.8-6.7).
The matrix phase has grains with size about 5 µm.
Matrix lattice parameter and the relative level of matrix microstresses (a) and the hardness (b) of the Al-2% Fe alloy depending on the number of revolutions It was show that upon annealing at temperatures below 250 o C (for Al-Zr alloy) and 300o C (for AlFe and Al-Cr alloys) the grains do not grow above 300 nm.
The most intense grain growth begins at temperatures above 350 oC and 450 o C the grain size reaches 1.5 µm.

As shown in Fig.2, during the traditional lapping (TL) process material removal rate increases along with the lapping speed, which is involved from that the bigger linear velocity makes the friction between workpiece and oilstones intense per unit time and number of effect grains increase.
And the effect of the acoustic cavitation of cooling emulsion and peening of detached grains contributes to material removal.
Influence of Grain Size on Surface Roughness.
In ultrasonic lapping the influence of grain size on surface roughness keeps to the same rule in traditional lapping.
It is clear that the surface quality using W5 grain is superior to that using W20 grain and it is improved with ultrasonic assistance.

Alloy development and grain size control
After isothermal forging the grain size is reduced to about 120µm because the borides formed on casting are broken up and pin grain boundaries during recystallisation and during grain growth.
The grain size found in ingots of Ti46Al8Nb1B is about 150µm and in this case appropriate thermomechanical processing can lead to grain refinement to produce grains of about 100µm [5].
This type of microstructure is developed because the massive gamma is full of crystal defects which increase the number of potential sites for the precipitation of alpha which can precipitate on all four {111} planes in the gamma, yielding the complex type of microstructure shown in Figure 2.
It is likely that pre-yield cracking will not be an issue in this type of alloy since it is very fine grained, with a grain size of about 10µm.