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In the process of stress relaxation, the material occur migration of dislocation and grain boundary sliding.
Besides, the cellular structure will grow in number and the slip’s space will increase while the amount will decrease. 3.2 The study on micro-mechanism.
And it had the character of low angle grain boundaries[5].
Under long-time stress, grain will nucleate in the stress concentration location and then grow up; movable dislocation will climb, slip and stretch out.
Near the crystal boundary and on the grain boundary, the same sign dislocation will arrange in parallel, and the opposite will cancel out.

SEM and microanalysis were used to evaluate grain sizes and to identify the different phases.
Two phases are clearly identified by atomic number contrast.
Coarsening of magnesium grains and the second phase particles are clearly observed.
This grain coarsening accounts for the lower hardness values measured in this alloy.
On the other hand, the higher volume fraction of second phases in the Mg94Ni3Y1.5CeMM1.5 alloy prevents significant grain growth of the magnesium grains, so hardness values after long-term exposures are higher.

As can be seen from it, firstly, the general corrosion occurred seriously in all three kinds of materials; Secondly, sample without boron had uneven surface, and its grain was prominent, its grain boundaries was clear, which indicated that intergranular corrosion seriously occurred in the sample; the samples containing boron also had prominent grain on the surface, but it was smoother than that of the sample without boron.
Discussion The structures of the three samples were shown in Figure 4 by using SEM, as can be seen, Lath martensite being distributed in grain boundary and intragranular of ferrite was found in sample without B element and the lamellar pearlite was not found in the entire field (Fig.4(a)(e)).
Besides lath martensite, the lamellar structures that were similar to pearlite appeared in the intragranular and at the edge of lath martensite at grain boundary in the samples containing B (Fig. 4(f)-containing 16 ppm B, (g)-containing 26 ppm B).After the statistics of metallographic analysis, it was found that the content of non-ferritic structure in the sample without B was far more than that of the sample containing B.
The reason why Pearlite structure appeared in the stainless steel with B is that, on one hand, the trace boron makes the eutectoid point move left, which makes the casting in the cooling process tend to form pearlite structure and other products decomposed by the supercooled austenite [7,8], on the other hand, because of the distortion energy resulted from the atomic size of boron, boron can often segregate in grain boundaries, which indicates that boron is more likely to be absorbed in grain boundaries than carbon elements, thus the chromium carbide precipitation is reduced in grain boundaries, moreover, the interface energy between austenitic and ferrite phase is lower than grain boundaries energy of the ferrite, so it promotes the carbide precipitating in the phase interface preferentially[8], and results in carbon-rich austenite phase interface when austenite changed into martensite in the cooling process, thus boron contributed to the pearlite structure change.
First, Pearlite structure appeared in intragranular and the edge of lath martensite grain boundary of the stainless steel with B, because of this lamellar chromium carbide in the appearance of the phase interface, thereby reducing the chromium carbide precipitation at the grain boundaries,making the intergranular corrosion tendency reduced; Second, it can be found that the intergranular corrosion of the materials are mainly due to the corrosion of the lath martensite at high stresses in grain boundary, which is often due to the high stress area turning into anode that can be corroded easily, and because of a small number non-ferrite structures in grain boundary, samples containing B are less corrosive.

At the beginning of the trial, the bed surface was smooth, when the velocity increased, the bed face appeared little sand waves, like small ridge, increase velocity again, the sand grain increased, formed sand waves.
In order to observe the change rule of the starting velocity easily, the experiments fit the existed data, and take the grain size and water depth as the independent variable, then the few motional velocity as dependent variable.
Uki deduced from the experimental data ，where y is 1/6，the formula（4）can be shown as the relationship of the starting velocity and the water depth: （5） where：Km is the function of the grain size of the model sand，its value can be seen in table 3.
Take the median particle diameter of 0.017 mm as the boundary，the bigger the grain size, the faster the starting velocity；if the grain size become finer, the starting velocity also increases to some extent.
As the Km always changes, it is hard to reflect the starting velocity of Pseudochark precisely by applying the formula(5), hence the curve-fitting method to Uki and d is to reflect the different grain size starting velocity.

The rutile peaks are quite sharp which indicate that grain size of the rutile grains increased significantly upon calcinations.
The results indicate that there is a decrease in the grain sizes of anatase when Ta is present as dopant.
Furthermore for the undoped samples, the grain growth is more than Ta doped samples at temperature above 500 oC.
on the average grain size(nm) of TiO2 anatase phase Sample As synthesized 500 oC 600 oC 650 oC 700 oC 750 oC undoped 9 19 48 70 - - 0.5 at % Ta 8 19 33 43 49, 90* > 100* 1.0 at % Ta 6 21 31 60 70 - 1.5 at % Ta 5 19 35 45 58, 100* 37, >100* *Average grain sizes of rutile calculated from the peak intensity (110) of the rutile Table 2 shows the lattice constants a & c of undoped and Ta doped samples.
Ismat, Journal of Nanoscience and Nanotechnology, Volume 8, Number 5, (2008), p. 2410 [3] Z.Ding, X.Hu, G.Q.Lu, P.L.Yue, P.F.Greenfield, Langmuir 16, (2000),p.6216 [4] A.

Grain displacement in an elastic adhesive results in accelerated edge blunting, more frequent grain breakdown, increased wear of gear hones.
In practice, due to penetration of abrasive grains into metal, wear and running-in of the tool material (event with its infinite stiffness) during operation, the contact takes place along a small ellipse-shaped area [6].
The contact pattern (machining) area — along with specific sliding — is one of the most critical parameters describing the gear hone operating conditions, demonstrating active influence of a particular amount of abrasive grains on the machining capacity, surface quality, and gear accuracy.
In case of machining by elastic gear hones, the positions of grain peaks are set on the machined surface, the height difference of the cutting profiles is decreased, the distance between peaks is reduced, the surface and grain interaction time increases.
The number of grain peaks per unit of a machined surface increases.

Owing to the low Zr content, the microstructure became recrystallized during extrusion with an average grain size of 110 µm (ASTM grain size number 3-4), and only a small elongation of the grains in the longitudinal direction was observed.
The microscopical investigations reveal a deformation induced surface roughening effect, known as "orange peel surface", originating from the out-of-plane movement of the less restricted surface grains.
In each grain, slip lines belonging to one or two crystallographic slip systems are observed.
SEM investigations show that the grain boundaries are mostly non-detached and that small cracks instead have formed inside the grains.
The cracks are usually confined to the grain in which they nucleate.

Introduction Mechanical properties of carbon nano-tube (CNTs )have attracted the attention of a large number of researchers since their discovery in 1991[1-2].
Many research data show that[11] when pure Al grain size reach to nanoscale, its strength and hardness improved greatly.
The diffraction peak became widen mainly due to the grain refining and the increase of the microstrain.
Add the CNTs in the Al matrix hinder the migration of dislocation in the grain boundary.
The grain size of Al is 46.4nm for milling of 2.5h.

It has been reported that the addition of Al element can improve the corrosion resistance of Mg alloys, a small number of Ca, Zn, Mn and a very small amount of low toxicity rare earth elements can retard the biodegradation of magnesium alloys [5, 9].
The EDS analysis results indicated that the grain boundaries (GBs) are rich in Al and Ca (Fig. 2a).
It can be seen that intergranular corrosion occurs, i.e. the α-matrix was deeply attacked along the grain boundaries such that intermetallic compounds (Mg,Al)2Ca survived.
In addition, pitting corrosion was also found in α-matrix or grain interiors.
Conclusions (1) Magnesium alloy AX53 is characterized by α-Mg and intermetallic compound (Mg, Al)2Ca along grain boundaries and small amount of AlMn phases in the grain interior

Its grains are hard (about 6), though brittle.
However, use of lightweight ceramics can be beneficial in a number of applications, especially as construction materials.
The densities of ground samples were different for the density was affected by the grain size of the fraction; coarser fractions had lower density due to the additional space among the grains.
The grain surfaces seemed to be affected more than their interior by the presence of borax.
The tests were carried out as a function of composition, grain size, temperature and time of firing.