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Fig. 6 Microstructure of aluminium after ECAP (sample W8) Fig. 7 Characteristic range of recrystallized grains (sample W8) However in the structure of ECAP processed material there are areas with a coarse grain structure (Fig. 7).
These large grains could have been formed as a result of dynamic recovery or recrystallization during the plastic deformation process.
It is apparent that the macrostructure became more homogeneous as the number of passes increased.
This resulted in a more homogeneous microstructure and a larger degree of grain refinement.
• Increasing the number of passes through the die increased the homogeneity ot the macrostructure

As can be seen that the number of PSPs present fine block, whilst the equivalent diameter of PSPs is 20~30 μm.
A large number of α-Al grains in smaller diameter are surrounded by the liquid phase, while those with larger diameter display a spherical of plate-like shape.
When holding time is elongated to 2400 s (Fig. 5(d)), the number of PSPs with smaller diameter continues to decrease.
Part of PSPs and α-Al15(Fe,Mn)3Si2 particles distribute around α-Al grains, while the other part distribute in internal α-Al grains.
Globular α-Al phases grow in the way of Oswald [9-10], that is, the grains in larger and in smaller diameter are combined and spherized to new globular grains.

They postulated that the matrix was eroded from around the grain until the working height was reached and this protrusion was maintained until the grain was fractured.
Diamond concentration refers to the number of abrasives per unit volume in the bond matrix.
Lower concentration may result in only a smaller number of diamond grains remaining on the working surface and cause excessive diamond fracture due to overloading, thereby leading to poorer wear performance (see specimen 1).
Excessive wear flats can lead to much sawing heat and subsequently the number of pull-outs increased and the protrusion height was reduced.
The excessive diamond pull-outs may result in only a much smaller number of whole crystals and micro-fractured grain remaining on the working surface, causing much poorer wear performance and increased power consumption.

The grain meets the strong internal stress and generates a large number of the dislocations inevitably.
This uneven very likely to produce a large number of the dislocations’ movement along different slip plane, break the cutting of the room dislocation network and accelerate the movement of the dislocations.
Under the grain boundary segregation, the movement to the grain boundary dislocation further exacerbates the abnormal deformation of the grain boundary and produces a strong stress concentration, so only a small external force will induce the movement of the dislocations in the neighboring grains which means the slip occurs easily in the neighboring grains.
Of course, the different grain boundary and the different grain parts have different stress concentration degree and forms.
In the Fig.3 to Fig.6, the plastic deformation of the grain is obvious.

There are however, rounded grains, sharp, elliptic, grain pointed to cutting bridges and these with different configurations.
Nevertheless, impact depth increases significantly with the grain sizes at first and then becomes slight even the grain size is important.
Indeed, the degrees of damage and cracks growth on glass surface are increased while increasing the number of impacts.
It can be clearly observed that the impact number and the depth of superficial defects increase during the sandblasting.
The results show that the state of the glass surface is degraded with the impacts number.

An attempt was made to predict the grain structure of conventionally cast ingots using the evaluated heterogeneous nucleation rate.
Gaussian distribution for heterogeneous nucleation sites was proposed by Thevoz et al. 14) , and this model has been widely used for the simulation of grain macrostructure formation.
Based on the marginal stability criterion, one obtains with where V is the growth velocity of a dendrite tip,�Γ is the Gibbs-Thomson coefficient, Pc is the Peclet number for solute diffusion, D is the diffusion coefficient in liquid, m is the liquidus slope, C0 is the initial concentration, k0 is the partition coefficient, Iv(Pc) is the Ivantsov function and G is the temperature gradient. ξC is a function of Peclet number and it close to unity at low growth velocity.
The relationship between the undercooling, ∆T, at the dendrite tip and the growth velocity can be calculated from the equations (5) and (6) by substituting an arbitral value of the Peclet number for equations (5) and (6).
Columnar grains grew from the chill surface at the bottom of the mold, and then columnar to equiaxed transition (CET) occurred at the upper region of the ingots.

An increase in the productivity of these operations can have dramatic positive economic effect, especially if the alternative is to hire more staff or increase the number of machines in the production.
The number of pores per unit area was given accordingly to the British Standard ISO4505:1978.
The solubility of WC in TiC is significant which leads to the grain coarsening of (W,Ti)C and grain refinement of WC caused by dissolution of WC small grains with reprecipitation on (W,Ti)C large grains, and coalescence involving grain boundary migration and co-operative solution-reprecipitation during sintering [8,18].
Grain growth inhibition of hardmetals during initial heat-up. 
Wittman, et al., WC grain growth and grain growth inhibition in nickel and iron binder hardmetals, Int.

When the film thickness was increased, the grain size was also increased.
First, when the film growth was continuous, the increased grain size was influenced by the forming of very small grain structures, which merged with neighboring grains [2].
(b) Measured grain size as a function of film thickness.
The variation of the reflection and color could be explained by the Drude model [4], which described its relation with the number of free electrons (Ne).
Although the number of Ne was indirectly measured from P(111) intensity in Fig. 1(b), its influence could be directly observed from the ZrN thin films which appeared darker at more than 300 nm.

Introduction Duplex stainless steels (DSSs) are stainless steels that contain a mixture of ferrite and austenite grains.
The grain shape was highly elongated in the rolling direction (Fig.1).
The stress response to strain cycling for the material in both conditions is compared in Fig. 2, where the tensile peak stress evolution of the stress-strain hysteresis loops is plotted versus the number of cycles.
The fracture surface of the aged samples has a brittle aspect and is essentially covered with transgranular brittle grain fracture. 0 500 1000 1500 2000 2500 3000 300 400 500 600 700 800 900 1000 Aged at 475 0 C, 200 hours As received Tensile Peak Stress, MPa Number of Cycles, N ∆ε∆ε∆ε∆εp= 0,35% ; 20 0 C Fig. 2 Cyclic behavior comparison between AR and aged samples cycled at room temperature with the same plastic strain range at half-life. .
The heavily deformed austenite grains would not offer a strong resistance to the further extension of the crack.

The coarser second phases are massed up at the grain boundaries of the center layer while those are crushed into smaller particles in the surface layer.
Nowadays, large machined structures are used to reduce the number of components and joints, and the thick aluminum alloy plates are manufactured to meet the requirements.
As shown in Fig 1, the grain morphology in the surface and center layer is different while the second phase particles are distributed along the grain boundaries.
The coarse grains with 65μm mean width are present in the center layer, while the stripped grains with 20 μm mean width appear in the surface layer.
But all grains are elongated along the rolling direction even after the solution-aging treatment.