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A large number of twins are seen at quasi-static strain rate and twin density decreases as the strain rate increases.
The refined grains are about 3 to 5 microns which is 3 to 4 times smaller than the grain size (15 to 20 microns) at quasi-static strain rate.
Voids seen within the grain boundaries also lower the strength of the alloy.
Smaller number of twins and coalescence of voids at higher strain rates seem to increase the ductility of the alloy.
At 2500s-1, the numbers of twins are decreased.

The mean particle and grain size was estimated by counting more than 100 particles or grains observed by using TEM or SEM.
But the grain size and relative density of samples sintered at 1200°C were larger than that sintered at 1100°C, due to higher sintering temperature promotes grain growth of BaTiO3 particles.
The dielectric temperature curves (Fig. 5) showed clearly the grain size dependence of the permittivity.
The sample with an average grain size of 0.70µm, which obtained from the powders calcined at 800˚C, had the highest dielectric constant of 2880 at 25˚C even though its relative density (90%) is lower than that with larger grain size and higher relative density.
Acknowledgements This work was supported by the '863' High Technology and Development Project of China under grant number 2001AA320501 and 2003AA302760, the Talent Training Program of the Beijing City under grant number 9558103500 and the Fok Ying Tung foundation under grant number 81063.

During this process, strip temperature is of great importance for controlling metallurgical transformation and grain size.
Introduction In cold-rolling process, the grains of steel are flatten, internally distorted and hardened by strain.
As the heating temperature rises, the microstructure and mechanical properties of steel go through three stages of transformation, recovery, recrystallization and grain growth.
Numerical results In this paper, the grid number in width direction is set to 20.
The number of tracer point along the length direction of strip is set to 300, so the grid Fourier number is about 10-3~10-4, depending on strip speed.

It can be observed that the addition of CNT significantly increased the overall number of load cycles to failure.
Fatigue cycles are normalized by dividing the current cycle number (N) by the number of cycles to failure (Nf).
As strain advanced, dislocation tangles moved gradually towards the grain boundaries.
(a&b) TEM images of dislocation activity near grain boundaries in the Al-0.5CNT composites.
Dislocations arranged themselves into neat arrays near the grain boundary (arrows).

When 1 mol% Li2O was added up, the number of abnormal grains and the grain size increased.
All the grains (the abnormal and the matrix grains) have faceted boundaries.
The 2 mol% Li2O sample consists mostly of equiaxed matrix grains and no abnormal grains are present.
These microstructural changes show the typical grain growth behavior of abnormal grain growth with the faceted interfaces.
Doping with Li2O caused an increase in the number of abnormal grains in the samples.

Large number of dislocations, twin boundaries and other defects that exist in the grain after deformation can increase the concentration of nucleation centers and diffusivity of solutes and therefore accelerate and promote the precipitation process.
The initial microstructures of the as-annealed GW83K alloy were equiaxed grains with average grain size 50µm and a small amount of residual second phase distributed in grain boundaries or intragranular area.
In this peak-aged condition the granular precipitates were observed distributed along the grain boundaries.
While heated to 500℃, mechanical twins were completely eliminated, replaced by the equiaxed grain, showing a typical recrystallized microstructure.
From another point of view is the increase of the number of precipitation phase, which is also consistent with previous findings.

The matrix grains deformed at 298K were cut apart into many small sub-grains with similar crystallographic orientation in the size of only 60-200 nm wide.
Very small amount of dislocation cells or bands observed in the specimens deformed at 76 K, although many sub-grains and areas containing dislocation network were found.
As the development of dislocation movement such as gliding or banding, the matrix grains are cut apart into many small districts called sub-grains in the size of only 60-200 nano-meters wide.
It is noticed that, a number of sub- grains around the martensite phase are shown in Fig. 4 (a), it is difficult to distinguish the martensite phase by the corresponding selected area diffraction patterns, which is demanding further analysis in the future research.
Very small amount of dislocation cells or bands observed in the specimens deformed at 76 K, although many sub-grains and areas containing dislocation network are found.

Local deformation at a grain boundary can be observed at the intersection of fatigue markings with the grain boundaries (GBs) after 50% of the expected fatigue life (8 x 104 cycles) at 450 MPa, see Fig.1(a).
The profile in Fig. 5(c) exhibits that the SBs are not homogeneously distributed across the grain.
The fine striations in the adjacent grain indicate the crack direction, marked by the white arrow.
Second, in grain B, intrusions roots, which identify SB cracking, can be seen.
As seen in Fig. 8, at constant stress amplitude, the recorded temperature – number of cycles T-N curves show that the temperature increases fast until a saturation state is reached, the level dependent on stress amplitude.

The initial number of mesh was 800.
The number of elements after remeshing was about 6000 with the minimum element size set to be 0.02 mm.
And user subroutine UGRAIN allows the user to calculate the typical grain size based upon the state of material.
Fig.3 shows the grain size evolution and distribution in simulated titanium alloy chips at different increments.
The grain size distribution shows the ASBs very clearly.

With hydrogen content increasing, the structure of TC21 production using hydrogenated powder by die forming and sintering gets well and the grain size becomes smaller.
With hydrogen content of increasing, the number of pores and the porosity showed a decreasing trend, the density of sintered body showed an increasing trend.
The number sintered body pores of TC21 powder with hydrogen content of 0.22 wt% was a minimum, the lamellar and needle-like structure was the thinnest, and the duplex structure was the maximum.
With hydrogen content increasing, the recrystallization appeared in grains of sintered body, grains boundary become vague, grains occurred breaking, new grains boundary become clear, duplex grains become more and more, grains size become smaller.
All of the phase transitions were favorable for recrystallization and grain size breaking of sintered body of hydrogenated titanium powder by die forming and sintering, as well as, it make for the sintered body has low porosity, refinement microstructure and higher performance.