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The other involves semi-hot forming, a process which leads to grain refinement [1].
The purpose of the first reduction at approximately 1000 °C is to refine austenite grains by re-crystallization.
It is evident that the resulting ferrite grain size is non-uniform.
This is why the mean ferrite grain size was determined separately for the coarse-grained and for the fine-grained regions.
Their ferrite grain size showed no substantial differences.

From the 3D image, the surface of the bilayers is non homogenous where irregular grain sizes were grown on the surface.
These irregular or abnormal grains were analyzed at the selected threshold of 86.63 nm (Z value).
The mean diameter of each grain is quite large which is 252 nm and therefore contribute to high surface roughness which the Ra value is 20.54 nm.
However, these irregular grains covers only 16% of total grain area whiles the remaining 84% are inhabited by smaller grains.
The different between individual crystallite and individual grain is that individual grain consists of a number of same repetitive ordering of individual crystallites.

In both cases ceramics with an the average grain size of about 300 nm and porosity of 5–50 % were obtained.
Intensive formation of ceramic structure begins at 1500 °C; grains converge to form a single frame.
Intensive grain growth occurs at 1600–1700 °C temperature.
At 1700 °C the size of pores is even larger, but the number of pores is small – virtually all the small pores have disappeared, and only closed pores in the grains remain (Fig. 7).
This could be due to grain growth and consolidation of pores.

While at 1293K, the bond line is nearly disappeared with the increasing of the number of the vanished voids.
The bonded interfacial microstructure is changed with the new-born grain appeared in some degree.
At the bonded interfacial region, the new-born grains were appeared by recrystallization.
In the specimen bonded for holding time of 12 minutes, the broken grain appeared.
And there appear the grains grew across the bonded interfacial line due to the atomic diffusion and boundary migration.

Traditionally, the main objective in conventional thermomechanical controlled processing (TMCP) of multiphase steels has been to refine the final grain size through (1) refining prior austenite grains, (2) increasing grain boundary area per unit volume by changing the grain shape, e.g., pancaking, and (3) increasing boundaries [7].
The austenite grain size varies depending on the final process conditions.
These is important because the grain size of the austenite strongly affects both, the kinetic of subsequent austenite to martensite transformation (g→a’) and the martensite grain size, namely smaller austenite grains consequently lead to a refinement of martensite grains [10,11].
As the amount of deformation in this region increases, the number of nucleation sites at the austenite grain boundaries and within austenite grains increase.
Furthermore, the packet size of martensite is not only dependent on the prior austenite grain size, but as well on the grain substructure of the austenite grains.

Unlike the FC model, for which the local strains in the grains are considered to be equal to the macroscopic strain applied to the polycrystal, the SC formulation allows each grain to deform differently, according to its directional properties and the strength of the interaction between the grain and its surroundings.
The properties of the HEM are not known in advance because they result from an average of the individual grain behaviors, once convergence is achieved.
An initially random texture, described by 1000 equiaxed grains was assumed.
To carry out our investigation, we modeled different texture intensities by spreading the grain orientations around the ideal {100}<001>.
For the cube set of textures, the number of individual orientations was set in order to obtain an adequate representation of a uniform distribution.

XRD and Atomic Force Microscopy (AFM) characterization reveal that the grains are nano-sized.
Using the Debye-Scherrer equation [5], the grain size has been estimated and has the value of about 33 nm.
The microstructure, such as grain size and surface roughness, has an important role on the electrical properties of thin films.
Looking to the Raman spectra of the thin films, is possible to see a shift on A1(TO1) and A1(TO2) active modes to lower wave numbers.
The grain size estimated by XRD has the value of 33 nm, which is in very good agreement with the value obtained by AFM image.

Such a processing of pure metals and alloys usually results in well-developed deformation structures, involving nanocrystalline (NC) structures, and could accompanied by enhancement of their strength, as also of a number (balance) of physical and mechanical properties [18-21].
One of the main effects is caused by grain refinement under the alloy processing, starting from cast structure of an ingot.
Meanwhile, the initial structure of Zr modified alloy was presented by grains with close sizes (Fig. 1b), only θ (Al2Cu) excess phases with volume fractions 1.1±0.1 % (Fig. 2b) and Al3Zr precipitates 10-50 nm in size inside grains (Fig. 3e).
Cryorolling led to thinning and subdivision of initial grains, decreasing the distances between these sites.
As a result, density of particles along grain boundaries and on perpendicular contact surface increased.

We obtained the corundum-zirconium ceramic with the grain size 0.35-0.5 μm and the coherent-scattering regions of 0.050-0.120 μm, possessing microhardness 10.6-12.9 GPа and crack-resistance 5.5-7.8 MPа·m1/2.
However, nanopowders have a number of peculiarities: active adsorption of impurity atoms from atmosphere, spontaneous agglomeration, and high interparticle friction.
The necessary condition of stabilizing high-temperature modification is application of the powder with ultra-dispersed (nano-) structure of grains [5].
At thermal sintering of compacts we have obtained the ceramic with the grain size of 0.35-0.5 μm and CSR 0.050-0.120 μm, possessing microhardness 10.6-12.9 GPa and crack resistance 5.5-7.8 MPa·m1/2.
A small size of the grain and crystallites, high value of microhardness are evidence of low structure imperfection.

In fast firing, the dissolution of larger quartz grains during firing is expected to be small due to the formation of dissolution rim around the grains which has a high content of silica and high viscosity.
The difference in thermal expansion coefficients between the glassy matrix and quartz grain inherently generates a residual stress.
The critical internal stress results in microcraks through glassy phase, around quartz grains and even within the quartz grains.
It shows the number of specimens tested and the mean value of KIc and σf obtained, together with the standard deviation.
These numbers are very close to those reported by other authors.