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Contrast to the conventional IF steel, the super fine grain steel has super fine grains and gives excellent press-formability such as low yield strength, high r-value (the plastic strain ratio) .
The fine precipitates are hardly observed close to the precipitation free zone(PFZ) besides the small numbers of coarser precipitates.
The little precipitates were apparently observed to be located in one side of grain boundary.
It is inferred that precipitates nearby the grain boundaries is to be formed during the grain growth after recrystallization because the shape of this region is intimate to the grain boundary of recrystallized grains.
Therefore, it is inferred that the arrays of coarse precipitates parallel to the grain boundaries as shown in Fig.4 which shows the trace of the grain boundaries.

CDRX is a process of dislocations continuing to gather to the small-angle grain boundaries, becoming to large-angle grain boundaries, and then forming fine grains during the deformation of metal [4].
However, the grain refinement in the piston pin holes is more obvious, the grain is refined to 13 μm and the refining rate is about 67.5%(shown in Fig.5a, 5b and 5c).This is attributed to the longitudinal extrusion, during which the deformation of the piston skirt processed by backward extrusion is intense, the severe deformation energy leads to a large number of tangly dislocations appearing in the piston skirt, which arises a big stress field between these dislocations.
Then these dislocations interact and rearrange to form a subgrain structure, and the subboundaries furtherly evolve into small-angle grain boundaries and large-angle grain boundaries, thus causing CDRX and refining grain.
The grain refinement of piston pin holes is more obvious, the grain is refined to 13 μm and the refining rate is about 67.5%
Application status of hot deformation metal grain size predicted[J].

The main reason is that the size of the inherent crack in the material depends on the grain size.
Hexagonal boron nitride (h-BN) ceramics is one of the ceramic materials affected by grain size.
The flexural strength and fracture toughness of samples were tested at room temperature by a three-point bending method (AG-20KNIC, SHIMADZU, Japan), and the number of samples tested in the same condition was eight.
This also shows that the larger grain size is favorable for the directional alignment of flaked h-BN grains.
Furthermore, the local agglomeration of the grains is observed in h-BN ceramics, and the small h-BN grains did not achieve the better filling effect.

It has been shown that the grain size and the size of intermetallic phases and their distribution are strongly dependent on the ECAP process parameters, primarily on the number of passes through the ECAP die.
After low number of passes, the obtained structure is not fully homogenous.
Areas with larger grains and areas with smaller grains coexist in the structure; with increasing number of passes the homogeneity increases.
After low number of passes also large unchanged Mg17Al12 particles remain in the structure.
The microstructure of AZ91 depends on the number of ECAP passes and also on the initial size and morphology of Mg17Al12 precipitates.

Effect of Grain Size on Mechanical Properties of Mg-0.3at.
In contrast, good balance of strength and ductility was realized in fine grained specimens with grain sizes around 2~5 μm.
Mg has an anisotropic hexagonal close-packed (HCP) crystal structure, providing only a limited number of independent slip systems, resulting in low strength as well as poor formability at room temperature [2].
For example, Sandlöbes et al. [7] have shown that a coarse grained (grain size~40 μm) Mg-3wt.
After annealing at 300 oC for 60 min, a fine grained (FG) structure with a mean grain size of 2.13 μm was obtained (Fig. 3(d, e)).

And there are many grain yield forecast methods.
According to Markov chain, we can divide the data sequence into a number of different states, represented by, state transition only occurs at countable moment such as etc.
(1) Here, denotes the total number of emerged state, denotes the number of state transferring to statethrough step, is the number of states by, one step state transition probability matrix is as follows (4).
Calculating by the number of state, we obtain the step transition matrix as follow (9):
From Table 2, we predict the yield of grain of Guangxi by exploiting the parameter joint model.

Metal with very fine grain size has higher hardness and ductile than metal with coarse grain structure (Hall-Petch theory) [5].
These standard arrays stipulate the way of conducting the minimal number of experiments, which could give the full information of all the factors that affect the performance parameters.
Grain size on speciment doesn’t homogen.
Figure 2: Grain Size Distribution on aluminium after ECAP process Grain size homogienity index calculate from grain size along cross section with equation (1).
Ci is represent of homogneity, lower Ci indicated more homogen grain and higher Ci indicated less homogen grain.

In the white area is an abrasive grain.
Finally, a labeling processing is done to obtain the number of the abrasive grains and those positions in the image [Process J].
Here the number of the abrasive grains was 3817, the detected number was 3324, the undetected number was 493 and the false detected number was 314.
Next a distribution of the number of the abrasive grain at intervals of 1.5[mm] was shown in Fig.8.
It was confirmed that the area with a small number of the abrasives and many exist periodically in the measurement range.

The transition is strongly grain size dependent, with the time to the transition decreasing with grain size.
For sliding frictional contact, the time to the transition is dependent on a number of extrinsic variables (load and speed) and intrinsic material variables, principally grain size.
The grain size is reasonably fine, however, there is a significant distribution in grain size.
Firstly, there has been differential wear between grains.
This means that, for a given time of operation, there will be greater dislocation activity in larger grain materials, leading to greater rotation of the grains and greater stress concentrations on grain boundaries [1,2,6].

Based on the results of the thermodynamic analysis of a number of experimental data, and in the light of the Kaibyshev-Valiev discovery, the possibility of periodic formation of a liquid-like state in the nanoregions of extremely "non-equilibrium" grain boundaries and in other structural defect regions in metallic polycrystals during superplastic deformation and intense plastic deformation is considered.
It should be noted that according to a number of known data (e.g., those in [13]), the structure of high-angle grain boundaries in metallic materials has a heterogeneous character and includes even in the “equilibrium” state I (GB1) about 1 % of excess free volume [14].
Hence, the “GB sliding” mechanisms can be related to the mutual turning (cranking) of grains by means of some slippage along grain boundaries (GB3), which are in the liquid-like state III.
The “GB sliding” mechanisms can be related to the mutual turning (cranking) of grains during SSPD by means of some slippage along grain boundaries (GB3), which are in the liquid-like state III.
Diploma number 339, 1988.