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In the second step, new, imperfect grains are created by recrystallizing old, deformed grains.
In the final stage of grain development, controlled cooling initiates the growth of new grains.
As seen in the Fig.3(B) & Fig.4(B) grains are seen to be more equiaxed, During the process annealing, atoms migrate in the crystal lattice and the number of dislocations decreases.
Results of optical microstructures and SEM are well in agreement for grain morphology as well as grain size of Al grains.
The process of annealing alters the material's ductility and hardness as a result of atom migration in the crystal lattice and a decrease in the number of dislocation density at the grain boundary [17].

The grain size was measured by the linear intercept method counting 100 grains.
TEM pictures at different magnifications were recorded both with a CCD camera and on film for measuring of particle number density, average needle lengths, average cross section areas, and width of the precipitate free zone (PFZ) at grain boundaries.
The grain structure is recrystallised in all four alloys analyzed in this work.
The results from the linear intercept measurements counting 100 grains were close to 150 µm for all alloys.
Hardness vs. number density of hardening precipitates Figure 5.

Pneumatic Transport of Coarse Grain Particle using Air Mass Balance Model Abhisekh Mukherjee1,a, Mrinmoy Dhar2,b and Nilkanta Barman2,c* 1Department of Power Engineering, National Power Training Institute (E.R), Durgapur-713216, West Bengal, India 2 Department of Mechanical Engineering, Jadavpur University, Kolkata-700032, India aabhisekh.mukherjee@yahoo.com, bmrinmoy2310@gmail.com, cnilkanta@mech.jdvu.ac.in *Corresponding author Keywords: Pneumatic, air mass balance, alumina, pressure drop, mass flow rate.
In this work, the pneumatic transport of coarse grain particles (alumina) through a horizontal pipe is considered.
The assumptions invoked in the model are as follows: (i) the whole process is under isothermal condition, (ii) the flow of the mixture is compressible in nature, (iii) the velocity of gas-solid mixture is same as the velocity of compressed air, (iv) the flow is an one dimensional flow, (v) there is no bubbly or slug flow and (vi) the number of sections is kept very high (~1,00,000) to receive accurate results.
Nomenclature Symbol Description ρ Density P Pressure (bar) V Volume () Mass of air when solid and air is present in pipe (Kg) Mass of air when there is only air in pipe (Kg) Volume flow rate of compressed air Q Volume flow rate at normal condition Velocity at the inlet of pipe section (m/s) A Cross-section area of the pipe () F Calibration Factor l Length (m) dl Section of the length used (m) m Mass (Kg) Mass flow rate (Kg/s) t Time (sec) Pressure drop due to compressed air (bar) Pressure drop due to solid (bar) dP Total Pressure drop (bar) Re Reynolds Number K Absolute roughness of the pipe ( Friction factor Impact Factor Subscript Description Compressed air Atmospheric air Solid p Pipe References
[3] O.Molerus, U.Heucke, Pneumatic transport of coarse grained particles in horizontal pipes, Powder Technology. 102 (1999) 135-150

Micro-examination is performed for a number of purposes, most commonly it is carried out to assess the structure of material for quality purposes such as to ensures correct heat treatment is employed and detects unwanted phases and inclusion along with analyze of grain growth occurrence [7].
The grain size is bigger but there is no settlement of grains along a particular direction.
The grains started to group result in bigger grains.
The grains are grouped to form a bigger Pearlite grain.
The grains not only settle to form bigger grains but also follow an unpredictable alignment.

The average crystal grain size of sample TiC-2 was around 98 nm.
The coatings with fine crystal grains had many crystal grain boundaries, and it was possible that when hydrogen passed through a crystal grain boundary, the boundary served as a barrier to diffusion.
Solid solubility is the ratio of the number of hydrogen atoms to the number of normal lattice points, whereas the hydrogen concentration is proportional to the square root of the hydrogen gas pressure.
Muller, Grains and grain boundaries in single-layer graphene atomic patchwork quilts, Nature 469, (2011) 389-392
Feaugas, Grain Size and Grain-Boundary Effects on Diffusion and Trapping of Hydrogen in Pure Nickel, Acta Mater. 60, (2012) 6814-6828

From Figs. 1a and e, it can be seen that the microstructures of hot bands consisted of elongated grains.
The in-grain shear bands, which are inclined at the angles of ~30° to the rolling direction, can be observed in some grains, as shown in Fig. 1e.
After cold rolling, the microstructure consisted of elongated grains, Figs. 1c and g.
The average grain size of final sheet LTP was measured to be 20.2 μm, reduced by about 27.6% as compared to that of final sheet CP.
Fig. 4b shows the relationship between the mole numbers of C, N and Ti in the Ti(C, N) and temperature, which displays the sequence of precipitation and equilibrium mole numbers of precipitates.

Chen et al.[5] presented that the distribution of dislocations in mc-Si grown by directional solidification method was highly inhomogeneous from one grain to another, and high inhomogeneous dislocation distribution was also observed in individual grains.
These stacking faults within the individual grain were marked with black arrows.
Interestingly, There is a anther phenomenon could be found in the grain 2 at the top part of the ingot A, some dislocations are arrayed in the form of dislocation cluster marked with the red arrows, which start from the middle of grain and end at grain boundary, this phenomenon is similar to the result of CHEN et al.[5].
Different dislocation density is observed among the grain 1, grain2 and grain 3 at the top part of the ingot B, a small number of dislocations are sparsely distributed in grain 1 and grain 2, but the grain 3 is covered with densely populated dislocations, these phenomenon can also be discovered in the bottom part of the ingot B.
Some dislocation clusters marked with the red arrows are shown in grain 2(Fig.1(c)), which start from one grain boundary marked with the black arrows and end at another grain boundary.

It is demonstrated that band grains are stretched as strain increasing, and at the strain of 0.7, even some grains abrupted.
At a low strain rate of 10-3 s-1, the grains bulge out and a number of LABs appear inside the grains (Figs. 4a and b).
As the strain increasing to 0.7, the number of LABs almost remains the same.
Some HABs are generated in the deformed grains and form new grains (Fig. 4b).
Dislocations appear during deformation, migrate and accumulate into LABs, and then rotate into HABs, which form the grain boundaries of newly formed grains.

However, a large number of Mg alloys used for casting are confined to Mg-Al system such as AZ91 or AM60 alloys.
In this study, two microstructures have been studied; 1) having thermally unstable particles along grain boundaries and 2) having thermally stable particles along grain boundaries as well as within matrix.
It should be mentioned here that the grain boundary particles in MX have higher thermal stability than grain boundary Mg17Al12 particles in AZ91 [1].
In the case of squeeze cast AZ91 alloy, its large grain size overrode the detrimental effect of thermally unstable Mg17Al12 particles along grain boundaries.
Alloy Vol. % of 2nd phase particles Average grain size [µm] Average particle size (g.b.)

The results of OM exhibit that the dendrite precipitation occurs while the precipitate in grain boundary solutions as the temperature increasing and the grain coarsens immensely beyond 1000℃.
The size and depth of dimple decides the number of nucleation and the plastic of material when the steel fracture[3].Since the ferrite occur in the austenite matrix and the precipitations not completely form solid solution, the grain boundary segregation was more focused, therefore, the grain boundary strength has been weakened, it is easy to be fragment and to form the cracks, the cracks extend along the grain boundary and the specimen fracture along the grain boundary eventually. 900℃ 1050℃ 1150℃ Fig. 2 SEM result for tensile fracture of Mnl8Crl8 steel Metallographic observation.
Grain boundary is clear and thick, there are precipitations distributed in the transgranular at 800℃, When the temperature is up to 950℃, The grain boundary is shallow and thin.
The austenite grains grow rapidly and the grain boundary has been fusedat 1000℃.
At 1050℃, the grain continues to grow, grain boundaries disappear, leaving only regular arrangement of dendrite.