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A fine-grained material is harder and stronger than the one that is coarse because it has a greater total grain boundary area to impede dislocation motion [3].
The extruded magnesium alloy was processed by EX-ECAP, and it was found that the process could greatly refine the grains [13].Using the tube high pressure shearing technique, the magnesium alloy tube has been sheared under the hydraulic condition to produce the gradient ultra-fined grains [14].The AZ31 magnesium alloy thin-walled tubes with ultra-fined grains have been formed by tube extrusion [15].It has been proven that TES process can improve workability and strength of magnesium alloys by refining microstructures [16].
But the grain sizes of the tube prepared by TES process are obviously refined, the microstructures are more uniform after the TES process.
A large number of fine grains of about 6μm and some coarse grains of about 19μm have been found.
[11] Koike J, Ohyama R, Kobayashi T, et al., Grain-Boundary Sliding in AZ31 Magnesium Alloys at Room Temperature to 523 K.

Jeong et al. found that the wear rate of nickel with grain size of 13nm, approximately half the rate of wear of polycrystalline nickel with a grain size of 90 μm [7].
Consequently when the nucleation mechanism dominates the deposition process with a large number of nuclei generated on the substrate, the growth of nuclei and crystallites is strongly impeded [14].
The factors influencing the hardness of coatings included grain size, internal stress and the cavities.
Balasubramaniam, Effect of grain size on the tribological behavior of nanocrystalline nickel, Mater.
Qing, Effect of grain size on corrosion behavior of electrodeposited bulk nanocrystalline Ni, Trans.

Experimental details The reason for the short life of the conventional coating can be the grain size or segregation of carbides in the parent material Namely, high-carbon high-chromium steels are generally produced by the process of melting, followed by casting, followed by rolling (or forging), like common steels, and the steels thus produced contain a large number of so-called huge eutectic carbide grains segregated in such large size as not to be found in other steels, the huge carbide grains being peculiar to the high-carbon high-chromium systems.
MAXIMUM GRAINS OF MINERALS: 0.3 mm 6.
T.Alpas, High-temperature wear and deformation processes in metal matrix composites, Metallurgical and Materials Transactions A, Volume 27, Number 10, 3135-3148
Bailey, High-temperature wear of cemented tungsten carbide tools while machining particleboard and fiberboard, Journal of Wood Science, Volume 45, Number 6, 445-455
Patent number RO125760/2011

With the help of this method it is possible to create gradient materials with a hardened surface layer structure with ultra-fine grains.
A large number of intermetallic phase particles, solid solutions and mechanical mixtures are formed in the surface layer structure.
At deformation and fragmentation of a material during friction with high stress in a superficial layer a number of laminar and turbulent flows are formed.
Kaibyshev, Friction-stir welding of ultra-fine grained sheets of Al–Mg–Sc–Zr alloy, Mater.
Kaibyshev, Superplasticity of friction-stir welded Al–Mg–Sc sheets with ultrafine-grained microstructure, Mater.

EBSD NordlysNano detector by Oxford Instruments with analysis system has been used to determine orientation of specific grains and analyze local texture.
It is of a certain value for each CSL boundary: ∆Θ=15°/(Σn)1/2, where Σn is the number of coincidence sites under overlapping of three-dimensional crystal lattices.
In α-phase grains high dislocation density has been registered, expressed in large number of LABs, plotted for misorientation angles more than 1° (Fig. 1, f).
Probably, the first γ→α transformation nuclei are generated not within one austenitic grain, but in neighbouring grains, divided by crystallographically determined CSL Σ3 boundary, at the same time.
Karjalainen, Stability of grain-refined reversed structures in a 301LN austenitic stainless steel under cyclic loading, Mater.

However, a limited number of studies have been conducted concerning the formation of IGF in the HAZs.
The microstructure of weld metals and HAZs is known to be refined by different second particles, which may act as nucleation sites for IGF or pin austenite grains thereby preventing grain growth [3, 4].
A larger particle with the diameter of 0.5μm was found located in the triple junction of grain boundaries.
Moreover, the slower the cooling rate during solidification, the longer it takes for grain coarsening and the tinier the TiN particles for pinning prior austenite grain boundaries are[7].
In addition, the atomic numbers and atomic radius of Si, Ti and Mn are 14, 0.134nm, 22, 0.146nm, and 25, 0.130nm, respectively.

The consequent powders were mixed thoroughly with the PVA binder solution, and after granulation, a certain number of disk pellets of about 12 mm in diameter and 1 mm in height were pressed under a uniaxial pressure of around 20 MPa.
Fig. 2(a) and (b) show the scanning electron microscopy images of samples x=0 and x=0.175, and it is seen that the overall grain size of undoped samples is significantly higher (about 1 μm) than that in Nd-doped samples (about 0.5μm), suggesting that Sm doping content (x=0.175) of BFO inhibits the grain growth and leads to smaller grain size generally.
As Nd content increases continually to x=0.175, the mismatch between BiFeO3 and NdFeO3 lattice constant prevents the grains from growing big seeing Fig. 2(b), which introduces more grain boundaries.
These analyses enable one to resolve the contributions of various processes, for instance bulk effects and interfaces or the grains and grain boundaries in the frequency or temperature domain.
By splitting the contributions from grains and grain boundaries of the material, we have studied the complex impedance spectra.

Differential scanning calorimeter (DSC) from TA Instruments (model number: 2910) was used to determine the melting point of the materials.
The grain boundary region had a fairly distribution of Si3N4.
The morphology of Sn-0.7Cu solder and Si3N4 (black) as the reinforcement were uniformly distributed along the grain boundaries.
Reinforcement distribution between the grains will tend to hold the grains preventing from grain dislocation and retards the grain growth.
This could be attributed to: (1) pinning grain boundaries and thus impeding sliding of the grain boundaries, (2) the increase of dislocation densities and obstacles to restrict the motion of dislocation and (3) the hardening mechanism of the matrix and Si3N4 [11].

The opposite distribution is found on the normal direction, with a high number of (0002) planes and a nearly no (10-10) and (11-20) planes.
In the longitudinal direction, there is a large decrease in the number of (1010) grains and a rather complex variation of the number of (11-20) grains, whilst the fraction of (0002) grains increases very little.
The only difference between the two plates is a smaller number of (11-20) crystals along the longitudinal direction.
Under compression, grains whose c-axis are aligned to the applied stress tend to accumulate residual compressive stresses.
The presence of texture affects these stresses, since intergranular strains will tend to be small along directions where the grains are mostly oriented in [10-10] or [11-20] directions and no constraining c-axis grains.

In figure 1-a, a large number of platelets is observed within a former β-grain ; they are delimited by a contrast due to preferential etching of the precipitates.
The same prior β-grain is shown in figure 1-b in the form of a boundary map.
For each grain, only a few different orientations are present.
With increasing strain, lamellae start to "buckle" and a number of low angle boundaries develop through the microstructure.
However, some recrystallized grains appear during the test.