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This fact was supported by a number of AE detected in this period.
The number of Type-B AE increased stepwise, while Type-A AE increased at around 10 ks after Type-B increased.
We observed falling-off of grains along the surface SCC, as shown in (c).
This was formed by falling-off of the grains and not by anodic dissolution.
dissolution along chromium depleted grain boundary.

The addition of MWCNTs developed grain refinement by the FSP and grain size less than 500 nm was obtained [8].It has been clearly indicated that FSP reduces the grain size and increases the hardness value in MMCs [9-14].
It is revealed from Fig. 3b and 3c that, grain size of the specimens FSPed with SiC particles is remarkably smaller than grain size of base metal.
While the grain size of base metal was 40 µm.
As mentioned earlier, SC tool pine profile resulted in good separation of SiC particles and consequently increases the number of the SiC particles in SZ.
This is because of higher number of hard SiC particles acting as obstacle caused by good dispersion; this leads to higher resistance of surfaces against the sliding.

Secondly sample was burnished by metallographic sand paper after from number 1 to number 5, follow-on used polishing compound polishing, Finally samples were corroded by 5% of nitric acid alcohol.
And it also changes grain boundary's status and decreases interfacial tension and interfacial energy.
Firstly, CeO2 segregates in grain boundary through Diffusion Mechanism, Because of segregation of CeO2 can purify segregation of the impurity elements in grain boundary, then grain boundary is strengthened.
Fig.3.a is a map about friction coefficient and numbering of samples, Fig.3.b is a map about wear rate and numbering of samples.
Fig.3.a Map about friction coefficient and numbering of samples, Fig.3.b Map about wear rate and numbering of samples It is shown that wear resistance of samples with adding CeO2 were better.

On the right side of molten pool, detrimental Al-rich [100] dendrite is spontaneously susceptible to stray grain formation with equiaxed morphology.
The faster welding speed and the lower laser power are used, the smaller aluminum concentration and supersaturation ahead of dendrite tip are kinetically incurred to suppress columnar/equiaxed transition and stray grain formation with a number of thermometallurgical factors contribution to considerable microstructure amelioration and increasingly improve solidification cracking resistance and vice versa.
The latter importantly aggravates stray grain formation.
(1) where Γ is the Gibbs-Thomson coefficient, R is the dendrite tip radius, Pei is the Peclet number for i, mi is the liquidus slope, C0,i is the initial concentration for i, ki is the partition coefficient for i, ζc(Pei) is a function of the Peclet number, Iv(Pei) is the Ivantsov solution (i=Cr or Al) and Ghkl is the average temperature gradient nearby the dendrite tip.
Coexistence of three weld defects, including centerline grain boundary formation, stray grain formation and solidification cracking, are consequently suppressed for case of nonaxisymmetrical welding configuration.

Polycrystalline laser hosts have a number of advantages compared to single crystals, including higher dopant concentration, cheaper fabrication, and larger devices.
A number of studies have shown that microwave heating often results in superior microstructure with fewer trapped pores, cleaner grain boundaries, and smaller grain size than traditionally sintered materials.
The figure shows the larger micron-sized yttria grains surrounded by the submicron-sized alumina grains.
The grain structure appeared to be 2-5 µm.
The grain boundaries appear to be clean, although there are a number of trapped pores [see Fig. 3(c)].

It is due to the grain refinement.
These grain refinement techniques of using of inoculate elements, such as Ti, Zr, and Cr, were reported by the number of researcher, and were applied on high pure or commercial pure aluminium [2-5].
The microstructure on longitudinal section of the alloy tube shows an equiaxed grain structure, but their grain size was different with Ti content.
This significant grain refinement is due to role of Ti as a grain growth inhibitor.
(b) Variation of grain size distribution with Ti content.

The gamma to alpha phase transformation caused by the diffusion of Si and Al determines the grain size and morphology resulting in columnar grain growth.
The grain growth is apparently not affected by the diffusion process.
As silicon and aluminum diffuse from the coating the substrate is enriched in Si and Al and the grains transform into α phase.
These grains grow from the surface as a consequence of the diffusion flow resulting in a columnar grain morphology.
According to Szpunar [10], this decrease of magnetically favorable textures, such as (001)||RD, during the grain growth is caused by the different mobility of grains with these textures if compared with other textures, such as (111)||ND, which can grown much faster and consume the lower mobility grains.

By EBSD analysis, it was found that crystallographic variant selection was observed not only across those prior α/α grain boundaries, but also within the α grain interior.
It can be found that many slip bands in a phase grains and bulk b phase accumulated in triple grain junctions.
The dark grey grains refer the a grains and the light grey grains illustrate the different Euler angles of b phase.
From Fig. 1, it is sure that the matrix is the a phase, and lots of random b phase accumulated along grain boundaries and within prior a grains.
And it is sure that the orientation of b nucleating from a grain boundaries and within a grains is best described by the K-S orientation relationship.

Grain size and morphology results show that the compounds have clear grain morphology and also nanoscale grain sizes.
The uniformly grain growth and rounded shape grains with very clear surface morphology were observed.
It is obvious that MR values of nano-structured samples (NCMO & NBMO) will be higher compare to the bulk samples due to enhanced spin-polarized tunneling through the increased number of grain boundaries in nano-structured materials.
The grain size, structural symmetry and surface morphology can be governed by the calcination temperature.
The TEM and AFM results confirm that the nanoparticles of the NCMO & NBMO samples and grains are arranged in chains.

It conclude that some spherical shape phases of Ca2Mg6Zn3 distribute in the grain interior, and the other compounds continous precipitate at grain boundaries.
A fine-grained material is harder and stronger than the coarse one.
It is because that the fine-grained materials have the greater total grain boundary area which impedes dislocation motion.
The d is the average grain diameter, and are constants for a particular material.
Actually, the improvement of the yield strength is 10MPa, the numbers demonstrate that strengthening by grain size reduction is more, the strengthening mechanisms of the MZCxZr alloys is mainly the grain size reduction strengthening effect.