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These alloying elements in steel can be combined with carbon, nitrogen into a carbides, nitrides, and carbo-nitrides, which dissolve at high temperatures and precipitation at low temperatures.These compounds can obstruct the growing-up of original austenite grain during heating process and inhibit grain growth after recrystallization during the rolling process.
Table 3 Actual rolling process of experiment Sample numbers Austenitic recrystallization open rolling temperature (°C) Finishing temperature (°C) 1 1080 792 2 1100 805 3 1116 850 4 1122 855 5 1120 858 6 1126 895 Mechanical test Mechanical test results are shown in table 4.
As a result, it helps to refine grain and gain good microstructure in impact and tensile properties.
According to the formula of Hall-Patch, the yield strength of steel is determined by the grain size of ferrite.
That is to say, the finer the ferrite grain size is, the higher the yield strength of steel is.

It was found that the grain refinement layer was formed in the thickness of about 100μm .The dislocation density of LY12 aluminum alloy should be large increased after laser shocking because the accumulation of dislocation was appeared on the grain boundary.
With the laser energy density increased there formed subgrain structure and eventually generate ultra-fine grain.
(b) indicates that a large number of distinct accumulation of dislocation appeared in LY12 aluminum alloy.
Figure 2 shows grain refinement after laser impact observed from facula center.
From the photo it can be found that compared to matrix grain, a deeper hardening layer of about 100µm thick was produced on auminum alloy after laser impact, and corrosion-resisting property was greatly improved; this process may be caused by surface grain refinement, however, as for limited experimental conditions, refined grain boundary was not observed, which is to be studied and proved in future.

Under the vibration and shear of sloping plate, a relatively homogenous temperature field and composition filed are formed around some grains and are favorable for the direct growths of globular grains; meantime, dendrites formed under the vibration and shear are broken up and rounded gradually and better semisolid slurry is formed.
Large numbers of nucleus escaped the surface of sloping plate and entered into the interior of the melt and were favorable for the nucleus growth of globular crystal.
It can be seen from Fig.2 that the microstructure in position 1 of sloping plate mainly consists of dendrites and fine globular grains; the microstructure in position 2 mainly consists of rosette and globular grains; the microstructure in position 3 mainly consists of globular grains and near-globular grains.
Under the vibration and shear of sloping plate, nucleus escape ceaselessly the surface of sloping plate, and enter the interior of the melt, which is favorable for the formation of large numbers of nucleus inside the melt.
Under the shear and vibration of sloping plate, escaped grains not only move but also rotate [14].

For a particulate structure with particles of α-phase in a homogeneous distribution of β-phase, the contiguity of α-phase is given by the amount of α-α contacts and α-β contacts: αβαβαβαβ αααααααα αααααααα PLPL PL C ++++ ==== 2 2 (1) where PLαα is the number of α-α intersections and PLαβ is the number of α-β intersections.
CC presents the classical dendritic structure with coarse grains involved by eutectic phase, UR sample shows a very homogeneous and non-dendritic structure, with lower grain size, EMS sample shows fragmented structure with grain size similar to the UR condition.
Although the similar grain sizes of EMS and UR structures, the relationship between dimensions of primary particles and grains is higher in the UR samples than in the EMS ones, denoting lower number of primary particles within the grain in the UR.
A low misorientation among particles is expected, depending basically on the heat flow direction during solidification, facilitating the agglomeration in the semi-solid range, resulting in a higher number of particles within the grain.
The relationship primary particles/grain denotes the degree of interconnection of the primary particles in the structure: higher the relationship denotes a non-connected structures, one grain is one detached primary particle; lower the relationship denotes a very interconnected structure in which one grain contains several primary particles.

Effect of dip coated speed, number of coated cycles and annealed temperature on films properties were investigated.
The optimum condition for film preparation was at dip coated speed of 0.12 cm/s, number of coated cycles of 20 cycles and annealed temperature of 500 ºC.
Surface morphology of the TiO2 films formed grain that look like knobby shape.
Each grain was separate off and showed sharp grain boundary trace.
Surface morphology of TiO2 film formed grain in nano-grain size in the range of 10-50 nm.

It can be seen that the bSn grain structure in Sn-0.7Cu-0.05Ni contains multiple bSn grain orientations (colours in the Euler angle map of Figure 3(b)).
It can be seen that the bSn grains grow in a columnar mode from the Cu6Sn5 reaction layer and there are more bSn grains near the layer and a decreasing number of grains further away from the layer, which is indicative of grain selection by competitive growth from the nucleation site.
(c) bSn pole figures where colours give the orientation of the grains in (b).
Note that the grain structure is quite different in the Sn-0.7Cu-0.05Ni / Cu joint in Figure 4 and Sn-3Ag-0.5Cu / Cu joint in Figure 6 where multiple columnar grains grew in Figure 4 and two mutually-twinned grains grew in Figure 6.
A synchrotron imaging technique has been used to detect the nucleation and growth of primary Cu6Sn5 and EBSD has been applied to understand the differences in number of tin nucleation events and grain structures between the two solders.

Based on the analysis of a large number of literatures, this paper reviews the research status of the fatigue crack mechanism in China and abroad, and predicts the development direction in the future.
Grain boundary can prohibits PSB, and can produce the stress concentration leading to crack initiation and the formation of PSB in neighboring grain [14].
Zhang observes that, PSB can pass through the Low Angle Grain Boundary (LAGB), so no crack can produces at the grain boundary, as shown in figure 3.
When the misorientation of two grains is close to the orientations of the favorable slip plane within these two grains, high-angle grain boundary(HAGB) becomes an obstacle for the PSBs, which can lead to crack initiation.
(2-4) In whichis the stress in the process of fatigue load, N is the load cycle number, m is the Schmid constant containing PSB grain, L is the grain size, is neighboring grain size, h is the height of the PSB, d is the distance between two sides of the PSB, is the feature of the CSL model of GB, the first three parts of the formula are the energy expression in the continuum scale, the other parts are the contents related with atomic simulation.

They contain the chosen well-oriented grains without PSM (19, 136, 252 and 69) and their neighbour grains; b) three effective Schmid factor values obtained for each of the four selected "anomalous" grains.
Three microstructure models are compared: i) "classical Schmid factor approach": the stress tensor is homogeneous in the polycrystal ii) "grain-matrix model": only the selected 'anomalous' grain obeys crystalline elasticity whereas the neighbour grains and the matrix obey isotropic elasticity (no influence of the orientations of the neighbour grains) iii) "grain-neighbour grains-matrix model": not only the selected 'anomalous' grain but also its neighbour grains obey crystalline elasticity whereas the matrix obeys isotropic elasticity. 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5 grain 136 grain 252 grain 19 grain 69 equiaxed grain effective Schmid factor reference Schmid factor grain-matrix neighbour grains α [°] prim. slip µp Q geometry Grain 19 34 0.47 0.86 Small grain Grain 136 39 0.5 0.97 Small grain Grain 252 15 0.45 0.82 Small grain Grain 69 29 0.49 0.87 Thin twin loading axis FE Computations are carried out for each of the four
"Grain-neighbour grains-matrix model" iii).
They are close to the decrease computed for an equiaxed well-oriented grain surrounded by grains of random orientations and selecting the minimum effective factor among the computed values for a large number of sets of random orientations [6].
The orientations of the neighbouring grains are not taken into account ("grain-matrix model" ii)).

Large grain on the film surface hardly is found.
At low temperature, nucleation free energy declines and the number of the core increases.
This is helpful for grain to grow up.
On the other hand, it is considered that residual stress develops when newly deposited grains are attracted to one another during deposition, causing grain coalescence or “zipping” of the grain boundaries.
Thus, a number of microstructure variables are expected to influence the magnitude of residual stress generated by the grain size and coalescence mechanism.

The results show that at 1300℃ a large number of CAS2-Al2O3 caking formed the basic skeleton and some particles were not condensed.
At the same time, little Al2O3 grains are precipitated.
When the holding time extends to 1h, a large number of particles are formed and bonded, the sample porosity reduced and the density increased.
For 4h, the crystal boundaries intersect with each other, the caking body is evener, and a large number of Al2O3 is precipitated.
When the rate reaches 4℃/min, crystal grains are even and clear; grain interaction bond is close, but the blowhole rate increases.