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A polarized light Zeiss optical microscope was used for microstructural characterization and the grain size was measured following the ASTM standard E112-96.
Conventional DC casting produces a fully dendritic microstructure with an average grain size of 533 μm; MC-DC casting with high shearing intensity results in a fully rosette structure with an average grain size of 148 μm, and MC-DC casting with low shearing intensity results in a mixed microstructure with an average grain size of 181 μm.
(a) Micrograph of the top region of the sump from MC-DC casting showing a large number of rosettes in a narrow band (Region B) between the Pb-rich sump (Region C) and the large a-Mg dendrites (Region A); (b) Micrograph of the top region of the sump from conventional DC casting showing only dendrites.
The significant grain refinement in the MC-DC cast billet is due to the enhanced heterogeneous nucleation by intensive melt shearing [3], which disperses oxide films uniformly throughout the melt.
Fan, Grain refinement of DC cast magnesium alloys with intensive shearing, IOP Conf.

Films prepared at PO2=10 Pa had a high degree of (111) orientation and densely packed grains.
I(hkl) is the intensity of the (hkl) plane, I0(hkl) is the corresponding intensity in the Joint Committee on Powder Diffraction Standards data file, and N is the number of preferential growth orientations.
The film deposited at 5 Pa exhibits a uniform surface morphology with a low density of small grains.
For PO2=7.5 Pa, the grain size increases and the grains become more dense.
At 10 Pa and 12.5 Pa, the films have a high density of grains with irregular shapes and variable sizes that may result from the second phase observed in the XRD patterns [16, 17].

Introduction Recently, the number of developments directed on improving the existing types of materials and the creation of new functional materials [1] has significantly increased.
Comparison the suspension dispersion results obtained with bead and ball mills reveals that the grain size distribution in suspension obtained by dispersing for one hour in bead mill (d50 = 0,46 µm) can be reached in ball milling only after 48 hours.
As we can see (figure 3) an average grain size of the ceramic samples obtained after suspension dispersing by a bead mill is about 2 µm.
However after ball mill dispersing the sintered sample grains have cross sizes from 1 to 10 µm.
The average grain size in this case is 6 µm.

Rare earth elements are used as alloying additions in a number of Mg alloys.
The grain structure was revealed by mechanical polishing and subsequently etched with acetic-picral acid.
The microstructure of N0(AZ31) is shown in Fig.1(a), it is mainly composed of equiaxial grain with size of 10-50µ, and there are a few AlMn phase located in grain boundaries and grains interior.
After adding Nd, there exist some precipitations and they seem to have no effect on reduce grain size, as can be seen in Fig.1(b).

The discontinuous dynamic recrystallization (DDRX) mechanism is complex, it depends on the rheology of the material (strain hardening and dynamic recovery), and it involves the nucleation of new grains and the migration of grain boundaries as well.
This is partly because such alloys contain a large number of addition elements which may interact in a complicated way during hot deformation, thus requiring description of phenomena such as solute drag and Zener pinning, and their effect on grain-boundary migration [1].
A number of laws have been proposed for modeling this deformation range from dislocation concepts.
Piot et al., Modeling grain boundary mobility during dynamic recrystallization of metallic alloys, Mater.
Damamme, A grain scale approach for modeling steady-state discontinuous dynamic recrystallization, Acta Mater. 57 (2009) 1602-1612

Besides, the coarse grain causes low impact toughness of metal, especially at negative temperatures (steel cold brittleness threshold raises).
Several ways of grain refinement are known
• A steel microalloying with nitride- and carbide forming elements, such as vanadium, niobium, aluminum, titanium, boron, etc., that causes refinement of austenitic and real grain [2]
Simple analysis makes it possible to choose the 3rd way of steel grains refinement in view of its low cost and high performance.
Carried out researches were aimed to formation of fine grain structure of shape-rolled steel made of 09G2S low alloyed steels in the steel rolling conditions.

Compared to counterparts of Bi0.9La0.1FeO3 (BLFO) film, the grain refinement of all films is obvious.
BLFSO thin films show a uniform grain structure with a mean grain size of 80–100 nm.
In the Sc-doped BLFO thin films, grains are refining and packed more densely and the surface are smooth.
Moreover, compared to BLFO, the grain boundary tends to be ambiguous gradually with the increase of Sc doping level.
It has been reported that remanent polarization of perovskite-type ferroelectric material are affected by various factors, such as the displacement of polar ions, domain pinning by defects, and orientation [18-20], In this study, enhanced values of 2Pr seem to be related to Sc-substitution of Fe-sites by proper cations in BLFO thin films to effectively reduce the number of oxygen vacancies.

The grain refinement effect increases and then decreases with increasing pressure.
And these defects can provide a number of new nucleation sites, resulting in increasing neucleation efficiency[9].
The reason for this is that the atoms on the grain boundaries are disordered and many vacancies exist, resulting in the lower density and the higher energy than that in the grain.
And the grain with a higher potential would be protected as a cathode.
It is well known that the finer the grain of the alloy is, the larger the proportion of grain boundary area is.

The LSMO properties are modified by sintering temperature, which ruled the grain size and grain boundary properties [3, 4].
The SEM images showed LSMO samples have different grain size where the grain size increases with increasing sintering temperature.
This implies a decreasing number of grain boundaries by increasing sintering temperature, in agreement with Ref. [3].
Table 1 summarized the properties of grain size, µHC and MSP of LSMO samples.
We remark that MR values are not ruled by the physical properties i.e. grain size as reported in Refs. [3].

This causes redistribution of segregants if at all remained at the particle surfaces (deformation can displace these from grain boundary and disintegrate them to fine particles which easily dissolve inside the ferritic grains).
Thirdly pushing phosphorus into ferrite grain as solute and thereby discourages it to precipitate as phosphide along ferrite grain boundaries [10].
Microstructure test report from optical microscope shows porosity percentage to be 1.91, and the average grain size to be approximately 91 µm.
The alloy developed in the present investigation is free of any segregation of the alloying elements along the grain boundaries.
Hence a highly densified structure with large grains can be achieved.