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In the fig1(a), the ferrite grains are coarse，the grain boundary is not clear, and ferrite grains is shown as polygon and particle.
In the Fig1(c)，ferrite grain is distributed irregularity，the shape of ferrite grain are particle，polygon or block，and the grain boundary is clear.
The numbers of the island and fibrous martensite are few.
At the same time the number of precipitated second phase particles is significantly increasing with increasing reduction，and is the one of reason to restrain the growth of ferrite grain in the further.
It is found that the number of precipitated second phase particles are significantly increasing，the precipitated second phase particle is fined with increasing reduction.

The grain size also starts to become small.
It can be seen from Fig.2(a) that the grains is relatively coarse and the effect of grain refinement is not very good.
A large number of Ti and B enrich at the grain boundaries, which makes grain coarsen, dendrite arm spacing widen, and Al2Cu phase unevenly distribute.
However, when the holding temperature is above 740℃, a large number of Ti and B will enrich at grain boundaries.
With the increase of the holding time, a large number of Al3Ti phase and Al2Cu phase occur.

As a result, the toughness of welding seam increase with acicular ferrites number increases and acicular ferrites grain size decreases.
But in the HAZ, the grain growth coarsening is different with general grain growth.
High purity of CQ steel made the grain boundary migration and grain growth are easy.
It can be seen that there are a large number of inclusions, which was one of the important factors leading to cracks.
While grain growth in HAZ is serious, with average grain size 15μm, and unilateral width of heat affected zone 216um

Fine grain does not appear while the columnar crystal directly grow from the combination layer.This is different from the fine grain zone of the surface, columnar grain zone, equiaxed grain zone which are all formed during being casted.
This is when the laser clads, hexagonal structure α(Mg) solid solution of zone A and Mg matrix are fully coherent, while during the cooling process the grain grow directly as unmelt solid grains of the substrate surface as the nucleation center ,but limited number of the matrix grains result in a coarse columnar grains.
Massive dark figure is Mg2Si phase (a smaller number) by electron spectroscopy (EDS) analysis, we believe it reach zone B by convection and gravity.
Microstructure characteristics shows that a large number of dendrites located in the zone C.According to Electron Spectroscopy (EDS) analysis of figure 5, the coarse dendrites are Mg2Si phase and matrix is mainly β (Mg17Al12) facies.The molten Mg is reacted to Si of Al-Si eutectic alloy in zone C, then a large number of Mg2Si coarse dendrites is formed.
During the cooling process the melted Si separate out in the grain boundaries make the grain boundary coarsening.

The number of particles under 50nm increased gradually and the number of precipitates between 50~400 nm reduced significantly when the heating rate was increased to 50~300 °C/s.
There is enough time for grains to nucleate and grow up, and the recrystallization area fraction reaches 63% at the holding time of 10 s.
It is observed that the number density of precipitates is large.
Although the number of 50~150 nm increases too, the total number of particles between 50~400 nm nearly stays the same with that at 50 °C/s.
Then the number of precipitates under 50 nm is the most.

Grain refinement by inoculation with chemical grain refiners is an important and effective approach for mitigating such problems [1].
The search for new and effective grain refiners and methods for grain refinement still continues.
The discussion will be focused on the mechanisms of grain refinement. 2.
Such oxides may act as substrates for nucleation but are not effective for grain refinement due to their poor wetability and low number density.
All these factors contribute to the grain refinement. 5.

Whenever all grains have the same properties and the strain rate is uniform, every grain's history is the same, which leads to simple analytical calculations.
Eq. (3) means that any grain gives rise to one single grain during its life during the steady state.
Since a number of publications, including the original Derby papers [6], suggested , this led the present authors to choose in their DDRX model [1,2].
Cahn, The impurity-drag effect in grain boundary motion, Acta Metall. 10 (1962) 789-798
Derby, Dynamic recrystallization: the steady state grain size, Scripta Metall.

In this paper we present the object oriented finite element analysis of a real microstructure in order to obtain displacement and the deformation of grains and grain boundaries.
Sample with indication of the area for diamond pyramid hardness tests, where the micrographs were obtained One approach for investigating the microstructural behavior is to reduce the representation of microstructures at a small number of physical parameters, like grain dimension or porosity, and to develop a model depending of these.
Example of ferritic grain 50μm 50μm Example of pearlitic grain a) b) Fig. 2.
The boundary of the grain after automated selection Fig. 5.
The boundary of the grain after manual selection Fig. 3.

The paper studies the microstructure of two-phase ultrafine-grained titanium VT8M-1 alloy (Ti-5.7Al-3.8Mo-1.2Zr-1.3Sn), which was obtained by rotary swaging (RS).
The average size of grains/subgrains of the secondary α and β- phases was 0.3 µm [6].
Obviously, the reason is linked with silicides, which fix the grain boundaries and hinder the motion of dislocations during the creep tests.
Acknowledgements The reported study was funded by RFBR, project number 20-38-70105\20.
Semenova, Thermal Stability of Titanium Alloy VT8M-1 with Ultrafine-Grained Structure, Matec Web of Conferences, The 14th World Conf. on Titanium (Nantes)

The ultimate tensile strength increases with the number of CGP passes from 767 (solution annealed) to 1162 MPa (after 2 cycles), similarly, yield strength increases from 269 (as received) to 328 MPa (after 2 cycles).
Some researchers have successfully processed low carbon steels [17-19] via CGP for obtaining fine grained structured materials.
This graphs reflect the increase in hardness number with the increasing the number of CGP cycle.
Langdon,The process of grain refinement in equal-channel angular pressing, 46(9), (1998), Acta Mater., 3317-3331
Park, Constrained groove pressing and its application to grain refinement of aluminum, 328, (2002), Mater.