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Aluminium alloys are characterized by a number of advantageous properties, which include: low density, high relative strength, high electrical and thermal conductivity, ease of machining and good dumping features.
In the case of the alloy with addition of titanium the structure of the alloy was more fine-grained (Fig. 1c).
Near the mold wall has been observed the presence of large columnar grains.
Finer grains were visible in the middle of the ingot.
At the beginning crystallization runs close the mould walls, this results in a difference in grain size, a much smaller grains are present on the edge of samples and greater in the middle.

This leads to a significant reduction in the number of production stages and increased material yield by producing a near-net-shape product [5].
The use of larger powder particle sizes reduced the number of contact points per unit volume while finer particles are closely packed and offer strong resistance to applied pressure.
The shapes of the grains suggested that closely parked grains (necking) were formed within the microstructure.
Bonding joints were found between grains located at the grain boundaries within the microstructure.
Therefore, strengthening of the sintered alloys occurred both in the grains and along the grain boundaries.

A comparison between experimental results of grain size is shown.
The number of cutting increments m is therefore chosen to be greater than the order of the polynomial, i.e. m > n.
This work used n = 7 with 8 constants Ai and m = 9, this being the number of experimental slot cutting depths at which strain readings were collected.
In Fig. 6 shows the grain size results
Measurement of grain size in each section.

The sub-boundaries within DRX grains progressively disintegrate through dislocation climb and dislocation annihilation, which ultimately leads to the formation of dislocation-free grains, and the grain boundary migration gradually becomes slower.
In contrast, the substructure character of the DRX grains was remarkably different from the deformed matrix regardless of grain orientation.
The substructure characteristics of DRX grains were observed to be quantitatively different for grains corresponding to different orientation components.
Beyond 60 s, the grain size only changed slightly through normal grain growth (Fig. 4b).
The deformed matrix substructure was largely characterized by “organized”, banded subgrain arrangements with alternating misorientations, resulting from a limited number of active slip systems frequently concentrated on one slip plane.

Instead of propagating into grain directly, the crack goes on extending along the grain boundary between the grains.
And it moves ahead along the grain boundary all the way until it meets the next grain, and then it deflects again.
And the alloy with the addition of Er element is covered by a large number of tiny dispersed Al3(Er, Zr) precipitate particles, some of which were acted as a core that used to heterogeneous nucleation with the Mg, Zn and Al, as show in Fig. 3(c).
Usually, dislocations pile up easily in front of the grain boundary when move into the grain, because the grain boundary plays the part of an obstruction for the dislocation.
Akamatsu, Influence of scandium and zirconium on grain stability and superplastic ductilities in ultrafine-grained Al–Mg alloys, Acta Mater. 50 (2002) 553–564

In general, a number of routes have been employed to fabricate porous semiconducting BaTiO3.
The grain size of the ceramics was estimated using the line intersecting method.
TABLE 1: Density, porosity and grain size of the Sb-doped BaTiO3 added with graphite.
The presence of pores in the ceramics can cause the grain boundaries to be easily oxidized and consequently affect the electrical barrier height of grain boundaries.
This variation may also be attributed from the changes in the donor concentration of grains and the grain size.

When a grain is fully recovered, the orientation spread within a grain stays unchanged near 6 o .
While the orientation spread stays near 6 o for a fully recovered grain, a fully recrystallized grain is expected to have much lower orientation spread.
The preheat treatment was given to control variation of dispersoid particles in size and number.
Grain boundaries with 15 o and higher misorientation are drawn in Figure 1c to illustrate the grain structure.
Considering the grain structure illustrated by the grain boundaries, Al-Cu-Mg-Mn appears recovered but it is not conclusive.

The refined crystalline grains restrain the nucleation and expansion of micro cracks on grain boundary, which prevents materials from falling off in form of grain.
A large number of coarse carbides improve the brittleness, mircrohardness and crack sensitivity of the coating.
Finally they found that there were a large number of pores in the coating.
The refined crystalline grains restrain the nucleation and expansion of micro cracks on grain boundary, which prevents materials from falling off in form of grain.
Grain-size dependence of the wear of alumina[J].

Hardness of fusion zone increases with the depth. (5)A big difference of Average Grain Size is found in microstructure close to the fracture surface among S3557, S3556 and S3559.The greater the Average Grain Size is, the lower the CTOD value will appear.
Grain type as is shown in Fig.7 to Fig.9 is equiaxed blocky ferrite, but the sizes are different.
The size of grains in S3552B is the smallest of all B samples, while S35510B is secondary.
The larger the CTOD value is the smaller the Average Grain Size will be.
Table4 The Average Grain Sizes of S3557B, S3556B and S3559B Sample Number S3557B S3556B S3559B Average Grain Size 9.39 8.40 7.85 Rockwell hardness (HRA) of S35511A and S35511B is measured referring to EN10225:2009.

The fourth stage is called random welding orientation in which a number of lamellar colonies of random orientation developed in each composite particle.
Table1 shows the grain size and lattice strain of as-milled powders.
It is observed that in the process of milling, the grain size of powders decreased to nanoscale.
The increased grain boundaries not only enhanced the interfacial energy, but also accelerated the diffusion of element, it is known that the diffusion coefficient of an element at grain boundary is 20 times faster than in lattice.
In Ti50Al50 alloy, the grain size condition for formation of amorphous phase is £12nm.