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There were a few small ball shaped grains in the La-doped samples as shown in Fig. 2(b).
The presence of LaMnO3 with the perovskite structure inhibited the grain growth of the spinel phase.
In order to reduce grain size and the effective area of grain to grain contact, a greater porosity was produced.
Furthermore, as the amount of La2O3 in Mn0.75Ni1.25CuO4-xLa2O3 ceramics increased, the number of pores was increased.
Due to a typical polycrystalline of La-doped Mn-Ni-Cu-O ceramic, the resistivity of a sintered bulk could be affected by the grains, grain boundary and defects.

The nugget region, at the centre of TMAZ, has relatively small, equiaxed grains of 1-10 µm diameter.
Within the HAZ, there is continuous network of precipitates at the grain boundaries.
Conversely, on the left side of the corrosion band, i.e within the TMAZ, a large number of randomly distributed pits, of dimension about 50-300 µm, have developed.
In Fig. 9 b, it is clear that corrosion propagates along the grain boundaries.
Corrosion is associated with grain boundaries, where local microgalvanic action is established, due to the presence of continuous networks of copper and magnesium containing precipitates at grain boundaries within the HAZ.

The large number of experiments focused on metals-doped ZnO, there have been numerous thin films growth reports for Al [5], Ga [6], Mg [7], Cu [8] doped ZnO.
According to the full width at half maximum (FWHM) of the (002) reflection line, the grain sizes are estimated among 15-18 nm.
AFM analysis suggests that the film was polycrystalline and consisted of grains with a grain size less than 25nm.
The AFM image indicates that the surface of Zn1-xMnxO film is relatively smooth and an average grain diameter is about 16nm, and the results obtained by AFM analysis is coincide with the results of the grain size calculated by the Debye–Scherrer formula.
The film had rather flat surfaces with the peak-to-tail roughness of about 25nm and an average grain diameter of about 17nm.

Besides the bulk dissolution of base metals into liquid Cu-P alloys, the grain boundary infiltration occurred at grain boundary.
This mainly because that the ionic radius of P is 1.06 and enough small compared with Cu(1.57)to diffuse into grain boundary at the brazing temperature and cause the dissolution of Cu along the grain boundary, and the content of P diffused in grain boundary in 0.89wt% While the filler metals region is composed of Ag-Cu binary eutectic and there are a few base metals dissolved into this fillers at interface when Cu-Ag alloys was selected (Fig.5d).
The way of dissolving Cu is only bulk dissolution and no grain boundary infiltration occurred as the radius of Ag atom is 1.75 which is larger than that of Cu.
As the ironic radius of P is enough small to diffuse into grain boundary to make grain boundary infiltration occurred.
The method of grain boundary infiltration combined with method of bulk dissolution accelerates the dissolution of Cu in Cu-P alloys (fig.6a).

This results from that there is much gap among the copper grains in the samples during the extrusion procedure of hot-press when the graphene content is relatively low, the graphene will fill the gap among the Cu grains in the samples.
On the other hand, the dimension of copper grains (secondary grains) in the experiment is relatively large (5~30μm), which will lead to the larger copper grains in the composites (primary grains).
According to the fine crystalline strengthening theory, the smaller the grain dimension is, the higher the fracture is.
The crack in the composites with larger grains will spread easily leading to the composite be damaged easily.
The aggregation extent of graphene, the compactness and the number of the free electrons made the electric conductivity and thermal conductivity decrease first and then increase comprehensively.

Beyond stage II the cell walls are replaced by sub-grain boundaries of average misorientation j, under which conditions the total dislocation density becomes:, where is a geometric constant of size 3.
The second terms in Eqs. 1 and 2 represent, respectively, the dynamic recovery effects on the internal dislocation density, ri, and the sub-grain size, d.
In addition to give the variation in dislocation density and sub-grain size with time during annealing, the model provides the yield stress, recrystallized grain size and fraction recrystallized as the main output.
When the fraction recrystallized, Xrex, is determined, the grain size in the recrystallized regions can be calculated as , where is the total number of nuclei.
The evolution of the microstructure variables is modelled by a set of four ordinary differential equations: (5) (6) (7) (8) (9) Here X(t) is the fraction recrystallized, r(t), the radius of spherical recrystallization grains, and M(t) the grain boundary mobility, Ua and URX are activation energies, css is an effective solid solution level, while are model parameters.

Many efforts had been made to develop creep resistant magnesium alloys, and a number of Mg-A1-Si (AS series) and Mg-A1-RE (RE, rare earth) (AE series) alloys were therefore developed in order to improve the high temperature strength capabilities (above 150) by suppressing the β-phase precipitation [3-6].
The morphology of AZ71E alloy is composed of a-Mg grains of about 10µm diameter and acicular-like or rod-like second phase — Al11Ce3 phase and β-Mg17Al12 phase finely crystallized both inside the grains and along the grain boundaries (Fig. 1a).
The microstructure of AZ91D consists of primary a-Mg grains with the grain boundaries decorated by large and discontinuous net-like β-Mg17Al12 phase precipitate (Fig.1b).
The grain size in AZ91D alloy is distinctly larger than that in AZ71E alloy, which implied that the addition of rare earth elements might effectively reduce the size of grain.
As for AZ71E alloy, the strengthening phases include Al11Ce3, Mg17Al12 and Al10Ce2Mn7; due to the high thermal stability and the low diffusion speed of rare earth (RE) elements in magnesium at elevated temperature, Al11Ce3 phase provides an effective barrier to the coarsening of the microstructure and this is considered to be an effective obstacle to grain boundary sliding and dislocation motion in the vicinity of the grain boundaries at high temperatures [5, 6].

The properties of Nd1-xSrxMnO3 manganites can be investigate using various number of doping [8].
The surface and grain size was able to identify using 10.000 times of magnification.
SEM images reveal that the dimensions of the grain samples are various.
The grain boundary of the sample can clearly be seen.
This suggest that inside a single grain, there exist a smaller crystallite.

Classical pressing technology implies a much larger number of operations leading to an increase in production costs.
Small areas with a larger grain size, up to 50 μm, appear here.
In zone B, some orientation of the grains along the pressing direction can be noted.
Here, too, after pressing, an oriented-directed recrystallized grain is observed.
Also noted is the fact of formation orientation of the grains along the direction of the pressing process in the metal after passing the die.

Based on the results, the microstructure of both components exhibited coarse grains plus lamellar and rounded intermetallic particles.
A number of samples were drawn by both parts in as-received condition.
For each aluminum alloy, nine composite micrographs were acquired in cross-section to calculate the average grain size.
In the T4 state, the microstructure of the two extruded parts consisted of coarse equiaxed grains with a great number of intermetallic particles uniformly distributed in the metal matrix (Fig. 2a and b).
· Irrespective of the heat treatment route, no changes were detected in the microstructure and average grain size