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The large black region in Figure 1(a) is α-Mg and Mg17Al12 forms a grey network structure along with the grain boundaries.
This indicates that there are larger numbers of secondary Mg2Sn particles existed, whereas the grey network of Mg17Al12 is dissolved mostly.
With longer ageing time, the lath-like and plate-like precipitation of Mg17Al12 and Mg2Sn phase are observed along with the grain boundary.
Thus there are only the tiny precipitation phases along the grain boundaries observed on T6 treated specimens.
In the present study, the discrete Mg17Al12 and Mg2Sn phases are mainly precipitated at the grain boundaries.

The evolution of dislocation populations accounting for restoration processes is given by: (2) where: t - time, – strain rate, D - austenite grain size, rcr – critical dislocation density for recrystallization, calculated as: (3) where: Z – Zener-Hollomon parameter, T – temperature, R – gas constant, a11, a12 – coefficients, a14 – activation energy.
The average free path for dislocations l, the recovery term A2 and the recrystallization term A3 in Eq. (2) are calculated as: (5) , , (6) where: a2 – self diffusion coefficient, a3 – activation energy for self-diffusion, a4 –coefficient of the grain boundary mobility, a5 – activation energy for grain boundary mobility, a6 – coefficient, a1, a13 – coefficients, T – temperature, R – gas constant.
The dimension of an optimization decision space is equal to the number of parameters to be identified, thus to improve the efficiency and reliability of identification sensitivity analysis was applied.
The SA results allow to reduce the number of identified parameters, i.e. the parameters of the lowest sensitivity indices were not identified, or the variations of these parameters in an optimization step is the highest.
Internal variable model (IVM) is suitable for materials when grain size is the parameter controlling yield stress during transient flow and applied when delay in response to changes of strain rate is observed.

SiC is a major industrial material with a considerable number of applications.
Experimental The number molecular weights of PCS (NUDT, China) used in this study was between 1,000~3,100.
It also presented that the grain size of β-SiC was several nanometers while there still existed free carbon in the coatings.
Summary The uniform dense SiC coatings on graphite could be obtained from the PVPD method of PCS when the number molecular weight of PCS was in the range of 1000~1500.
The coatings mainly contained β-SiC with grain size of several nanometers while there still existed free carbon in the coatings when the pyrolysis temperature was 1250°C.

As the sp3 fraction increases, the G-peak moves to higher wave-numbers and the ID/IG ratio decreases.
Evidently the grain size decreases with the introduction of interlayers.
Grain boundary hardening and grain boundary sliding are two mechanisms of the possibilities to change films hardness [16, 17].
On the other hand, softening of materials caused by grain boundary sliding is mainly attributed to the large amount of defects in the grain boundaries.
Both DLC bilayer films showed a decrease in grain size and Rms roughness.

The related parameters are listed as follow: the number of balls is 50 (stainless steel, hardness 48-52 HRC); the diameter of each ball is 10 mm; the ratio of ball to powder is 10:1; the milling speed is 200 rpm.
Nano-sized Al2O3 particles are seen not only in the copper matrix of Al2O3/Cu composite, but they are also embedded in the grain boundaries acting as an obstacle against the grain boundary movement to prevent the grain growth and provide very small grain size.
Fig. 5 (a) indicates that several grain boundaries are obvious.
Fig. 4 and Fig. 5 indicate that with the addition of Al2O3 powders, grain becomes finer and the amount of grain boundary increases.
Another reason for this phenomenon is due to the grain morphology.

Ultrafine grained/nano grained structured steels have also been produced successfully by multiple compression [10], high-pressure torsion (HPT) [11], equal channel angular pressing (ECAP) [12] and hydrostatic extrusion [13] techniques.
Comparing the grain size of the solution annealed with different rolled samples, there is a significant change in the grain sizes, and grains are found to be elongated in the direction of rolling.
Diffuse nature of grains with 70 and 90% reduction is a manifestation of severe distortion.
This graph reflect the increase in hardness number with the increasing the percentage reduction in thickness.
Ø With increase in percentage of reduction of the sample, there is a significant change in grain size and grain shape and character (elongated grains in direction of rolling and diffused nature of boundaries of grain boundaries).

The coarse grains of solid solution elongated in the extrusion direction were observed in 6082 alloy.
On the contrary, the solid solution in 6023 quenched alloy state had fine-grained equiaxed morphology with an average grain size of 8 µm.
The low number density of fine Mn-rich dispersive particles that are present in the 6082 alloy could be responsible for the massive growth of solid solution grains during solution annealing of 6082 alloy [19, 23].
The solid solution grain size of 6023 alloy was considerably smaller.
Within the solid solution grains, extremely fine and dense rod-like particles were present.

In literature [9] it was shown that coarse grains embedded in an otherwise fine-grained matrix can act as critical defects, significantly decreasing the plastic fracture strain of γ-TiAl based alloys at RT.
Below Tγ,solv also globular γ-grains have a positive effect on suppression of the grain growth as well as Ti-borides [11].
The microstructure after annealing in the (α+β+γ)-phase field region with air cooling (AC) consists of globular βo and γ-grains together with highly supersaturated α2-grains.
In contrast to this, after the second heat-treatment step, where the specimen was kept at 850°C for 6 hours, the TEM image evidences the presence of a large number of γ-lamellae (Fig. 4b).
The increase in γ-phase is ascribed to the formation of γ-lamellae within supersaturated α2-grains.

It is significant to analyze the temperature field of continuous casting with different processing parameters in order to reduce or control the crack numbers or cracking extent in billet.
When the temperature is higher, some grain begin to melt and the sample will fracture along grain.
Because the grain refinement, plastic also increase significantly.
(2) Metallographic organization is super fine-grain and contains equiaxial ferrite and pearlite within 850～1000℃.
Because the grain refinement, plastic also increase significantly

Thixoforming conditions Number of condition Slug temperature (oC) Ram speed (m/s) Casting pressure (MPa) Mold temperature (oC) a 1050 1.5 5 300 b 1050 1.5 9 300 c 1050 0.08 5 300 d 1050 0.08 9 300 e 1065 0.08 9 300 Thixoforming.
%Ag alloy to establish the practical thixoforming conditions, such as, the shape, size, distribution of globular grain and fraction liquid with holding temperature.
Table 2 shows the variation of fraction liquid and average diameter of globular grains with isothermal holding Table 2.
The average diameter of globular grain increases with holding time only [5, 6].
The globular grains were very coarse, and there was a Fig. 2.