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Microdiffraction patterns taken from the area about 2 µm2 demonstrated a number of grains separated by high-angle grain boundaries.
The resulting grain structure can be effective obstacle for the development of grain boundary sliding.
It is clear that the large grains forming during superplasticity result in more difficult accommodation of grain boundary sliding by nucleation, slip and annihilation of dislocation on grain boundaries.
The revealed changes in phase composition of the alloy can also lead to enhancement of grain boundary mobility and acceleration of grain growth process that increases the grain boundary sliding resistance.
The changes in phase composition can also results in increase of grain boundary mobility and acceleration of grain growth.

We measured the grain sizes by counting the number of grains intercepting each line using the following equation.
(number of cycles to failure = 11,050,521).
We counted the number of grains within the ODA.
This number includes grains crossing the ODA boundary.
(number of cycles to failure = 21,345,292).

Plasticity of Copper with small grain size Y.
It was observed that at intermediate grain size stress relaxation shifts from unit to partial dislocations both nucleated at grain-boundaries and finally in the extreme refinement of the grains a radical change occurs with relaxation at the grain-boundary regions.
The stress concentration depends on the number of dislocations in the pile up ; combining the pile up length to the grain size leads to the Hall-Petch law:τs ∝∝∝∝ Gb d , where τs is the yield strength.
(b) Ultrafine grains have grain size below the critical dislocation mean free path, though (c) pile-up of dislocations and grain-boundaries sources still exist.
The grains are separated by low, high angle grain boundaries and twins.

Equal-channel angular pressing (ECAP) is used to convert coarse grain into ultrafine grain (UFG).
It is clear that the grain structure is not homogeneous but a mixed one of coarse grains and relatively small grains.
It can be found that the microstructures after 4 passes in 100°, 110° and 120° die via route Bc still consist of a considerable number of large grains and an un-uniform grain structure.
Plot showing the effect of die angle on shear strain after different number of passes Indeed, the die angle has effect on the microstructure produced.
A large number of grains are initially in the so-called hard orientations with small Schmid factors and deformation is difficult in them.

Grain sizes were measured by intercept method.
When bubbles collapse acoustic streaming develops in the melt, distributing the nuclei into the surrounding liquid producing a significant number of nuclei in the molten alloy, thus promoting heterogeneous nucleation.
When cavitation develops, the shock waves generated by bubbles collapse lead to fragmentation of dendritic cells in the mushy zone, which are re-distributed throughout the melt by acoustic streaming, increasing the number of solidification nuclei.
So the turning point of grain size is 660 ºC.
And because of the high pressure pulses caused by the ultrasonic cavitation, the wettablity of large number of impurity particles, such as Al2O3 based intermetallic particles, will be improved by eliminating the gas absorbed on the particles and fill the melt in the micro cracks of the particles.

The larger grain size, the smaller crack growth rate, though the static strength was decreased with increase in grain size.
The influence of grain size on the crack growth is complex.
For example, ultra fine-grained carbon steels have an excellent crack growth resistance, though the resistance is not influenced by grain size in conventional grained steels [2].
The relation between the logarithms of a crack length and the number of cycle can be approximated by a straight line, when the crack length is small.
The larger grain size, the smaller crack growth rate, though the static strength was decreased with increase in grain size inversely.

Not only cedar pollen in Japan but grass and birch pollens in North Europe [1-4] actinomycetes and fungal spores in US [5, 6] cause allergic symptom, and the number of allergy sufferers increases all over the world.
grains and orbicle substance.
The room has no open window, and therefore the total number of pollen grains is conserved.
In the present study, removal efficiency is fraction of the number of removed pollen grains to all of traced particles that are distributed uniformly in the room.
The bottom numbers indicate the flow rate [m3/min] The alphabet S stands for the smaller device width of 400 mm and L stands for the larger divice width of 450 mm.

The three-stage bolt forming using the ultra-fine grained specimens was carried out to check formability of the material.
The improved mechanical strength achieved by the ECAE is due to grain refinement since strength of materials was known to be proportional to the reciprocal of the square root of the grain size according to the empirical Hall-Petch equation [4].
Recently, high strength M4 bolts were manufactured using the ultra-fine grained AA6061 processed by the ECAE without heat treatment and formability of the ultra-fine grained specimen was investigated by Choi et al. [9].
In experiments of the ECAE, three different routes A, Bc and C up to four passes were applied to investigate the effect of processing routes and the number of passes on microstructural change and its homogeneity.
However, Vickers microhardness value was more homogeneous in the ultra-fine grained bolt than in the conventional one.

Rods were subjected to ECAP using a die with a channel-intersection angle of F = 110° at a temperature of 400°C with the number of passes amounting to 8.
Ultra fine-grained (UFG) – ECAP; 3.
Annealing for 1, 10 and 100 hours results in the increase in the number of peaks at cooling and heating which attests to a multi-stage transformation in these states.
Due to this, no new peaks are formed during annealing of UFG and NC states at 400°С for a period from 1 to 100 hours and the number of MT steps remains the same.
The temperature is 40°С, number of cycles 20. a) CG state, b) after ECAP, c) after HPT and annealing 400°C, 1 hour Thus, grain refinement of Ni50.7Ti49.3 alloy with application of SPD techniques results in emergence of the pseudoelastic effect at a temperature close to that of a human body.

INFLUENCE OF GRAIN SIZE ON THE THERMAL DIFFUSIVITY OF Pt-SnO2 CERAMIC M.M.
The grain coarsening is mainly attributed to sintering [6].
In bigger grain size samples, phonons would encounter less number of grain boundaries, presenting a longer apparent mean free path.
As shown in Fig.4, the inclusion of 0.5 wt% Pt in SnO2 (Sample B) inhibits the grain growth as it produces smaller average grain size.
This can be attributed to the reduction in the number of grain boundaries blocking the heat flow path.