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The fine-grained structure guarantees excellent plastic properties as well as high impact toughness.
These steels were conventionally numbered: 225, 227 and 228 and their chemical compositions are presented in Table 4.
It is possible to notice small numbers of the laminated ferrite precipitated at the boarders of the primary austenite grains in case of lower temperatures of the end of the deformation (780 and 760oC) a small banding of the structure.
Innumerous precipitations of the carbides inside of the ferrite grains are also observed.
When cooling from the temperature of 800oC, grained ferrite with the precipitations of carbides was obtained, a small number of needle-like ferrite and the bainite-martensite islands (Fig. 4).

A novel process of ultrasonic-assisted underwater wet arc welding was proposed to improve the joint properties, a number of ultrasonic-assisted underwater welding experiments were then carried out, and the effects of pulse frequency on weld formation, joint hardness and microstructure were investigated.
To demonstrate the effectiveness of the above system, a number of ultrasonic-assisted underwater wet arc welding experiments were carried out at different pulse frequencies.
The overheated zone of joint locates in the high temperature range of solid phase lines, in which austenite grain grows seriously and widmanstatten structure readily occurs subject to the rapid cooling of water, thus the joint toughness becomes poor.
As arc ultrasonic occurs in underwater welding, the forced vibration of test piece accelerates the rate of heat conduction, which restrains the growth of austenite grain while promoting the transformation from austenite grain to pro-eutectoid ferrite, finally obtaining the fine uniform HAZ microstructure.
At the same time, the arc ultrasonic vibration yields an effective mechanical stirring on molten pool, thus refines the grain, and increases the rate of crystallization and the acicular ferrite.

In the polycrystalline material (metal, alloy) the main microstructural parameter is grain boundary – i.e. surface interface between individual grains.
In an undeformed state, the structure is isotropic, the grains have isometric dimension and grain boundaries are not oriented.
In case of plastic deformation of this isotropic structure the grains will take anisometric dimension and grain boundaries are oriented, as seen in Fig. 2.
From the relative number (number to unit of length) of parallel test lines intersections with grain boundaries (PL)P and perpendicular lines ones (PL)O was total relative surface area (SV)TOT of grains estimated according to Eq. 1.
Planar oriented part of relative surface area (SV)OR of grains was estimated according to Eq. 2.

The new grains with sizes ranging from 10 to 50 µm are arranged in clusters rather than being homogenously distributed.
Notice grains with sizes of about 3 µm arranged in clusters.
SEM does not allow differentiate recrystallized grains from the surrounding subgrain structure.
This map makes easier the identification of recrystallized grains (equiaxed morphology).
Grain clustering is also evident.

There are about 20 grains along x,y axises,500 grains in total, and the initial grain size is about 50 um.
There are about 10 grains along x, y axes respectively and totally 100 grains in the model.
Each grain was subdivided by the grid set as shown in Fig.3 (a).
The number of nodes doubles during the process of dragging, but it remains unchanged while the prism being subdivided into tetrahedrons, as shown in Fig.3 (b).
Step 3, Drew the external boundary form 3D volume meshing of each grain to form the grain boundaries, then subdivided them with Quadrilateral.

Then, the twins originate in ERX grains.
The g¢ phases of the DD6 alloy have a solution temperature of approximately 1315°C [2], thus at 1100°C, a large number of g¢ phases still exist, as shown in Fig. 5.
Fully ERX grains nucleated after standard heat treatment.
And the twins occurred in fully ERX grains.
This effect prevents twins forming in cellular grains.

During the sintering process, the formation and growth of elongated β-Si3N4 grains are affected by some factors, such as the number of the β-Si3N4 nuclei, the intergranular space and the liquid for the growth of nuclei.
The amount of β-Si3N4 grains varied from 0 to 8 wt.%.
The reasons was explained as follows: the grain size difference between nuclei and matrix grains was large, the grain growth driving force for nuclei might be high, causing selective growth of nuclei.
Elongated grains could grow to higher aspect ratio when the number of β-nuclei provided by the starting powders was not too great[8].
Further growth of large grains was then possibly inhibited, and the length and the aspect ratio of grains were limited[8].

- the Miller Test based on ASTM test [6] allows to determine of SAR (Slurry Abrasion Response) number during the wear in slurry.
The comparative results of Miller Test and values of SAR number for investigated materials.
The wear proceeded not only by alumina grain crushing, but also by weakening of grains boundaries and whole grains removing, as a result.
As an effect whole grains or grains agglomerates could be removed.
This counteracts too fast grain boundary erosion.

Taking this into account, in this article we have developed methods for modeling grain geometry, grain boundary surface and geometry of grain contacts of doped BaTiO3-ceramics.
The small-grained microstructure, with the grains tending to form clusters, was observed.
Denote the grain by G.
Choose wi such that h(T, T*) < e, where e is a given positive number and h is the Hausdorff distance.
Conclusion In this article we have developed methods for modeling grain geometry, grain boundary surface and geometry of grain contacts of doped BaTiO3.

Three different casting process parameters were specifically designed The number (Table 1.) is poured into test bar with residual size, and the main chemical composition measured by direct reading spectrometer is shown in Table 2.
Serial number Alloy Shell temperature (℃) Pouring temperature (℃) 1 K4169 950 1410 2 950 1460 3 1050 1500 Table 2.
It can be seen from the figure that the alloy structure has a typical dendrite morphology, and there are a large number of island-like Laves phases between the dendrites, which are continuously distributed, as shown in Fig. 2(c).
It can be seen from Fig. 3(b) that after heat treatment of group B, the Laves phase and the needle like δ phase around the dendrite and at the grain boundary are basically eliminated, and only a small amount of Laves phase and MC type carbide are left.
After heat treatment in Group F, a large number of Laves hard and brittle phases formed by segregation of Nb elements remained between the dendrites.