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And the grain size was 200nm when the KNN powders was synthesized at 700℃.
The powders grain cannot grew up since the grain surface is stable [24].
With the temperature increasing to 800℃, the grain size grew up to 2μm.
The grain growth is consistent with Ostwald ripening.
(°C) Fig.9 Atomic number of the KNN powders sintered at different temperature (700℃, 800℃, 900℃) The amounts of Na, K and Nbatomic ratio in typical sample calcined at different temperatures(700℃, 800℃, 900℃) were measured by XRF in Fig.9.

During the present study, needle like grains of hematite have been observed within the top layers of a number of external oxide scales formed during simulated reheat of 316L stainless steel.
A number of recently published papers have shown that EBSD is an effective method for characterising scales formed on mild steels [7, 8] and more recently on stainless steels [9].
This would suggest that formation of the needles and the hematite grains at the grain boundaries are related.
It shows that the three needle containing spinel grains are of differing orientations to one another and that the needle like grains also differ not only to their parent grain but also to the needles formed in other spinel grains.
At 1300°C the needle like grains all have a similar misorientation angle to their parent grains of approximately 56°.

A typical print out of the surface roughness of Al – 4 %Cu specimen Results and Discussion Effect of the Number of Rolling Passes on the Grain Size of Al and Al- 4 % Cu.
Effect of rolling passes on the grain size of Al Pass Grain size µm 0 120 1 63.2 2 104.5 3 120.2 (a) (b) (c) (d) Fig. 2.
Effect of the number of passes on the grain size of commercially pure A at 200X.
Effect of rolling passes on the grain size of Al Pass Grain size µm 0 94.9 µm 1 114.5 2 104.5 3 79.9 (a) (b) (c) (d) Fig. 3.
Photomicrographs of Al - 4 % Cu showing variation of its general microstructure and grain size with the number of passes at 200X Effect of the Rolling Process on Vicker’s Microhardness.

Thus the pinning role exerted by the precipitates on the boundary of the austenite grains is weakened or even lost, which results in the growth of the austenite grains to form a so-called coarse-grain zone.
When multi-pass welding is applied to pipeline steel, there exists the Unchanged Coarse-grain HAZ, the Critical reheated Coarse-grain HAZ and the Sub-critical reheated Coarse-grain HAZ in the HAZ.
Utilizing the non-metallic inclusions within the austenite grains, which can promote the nucleation of intra-granular ferrite and refine the grain size, has become an important method to improve the strength and toughness of the HAZ.
The present study focuses on the nucleation of intra-granular ferrite and its sympathetic nucleation in the HAZ of X80 pipeline steel, which can promote the refining of grain size in the coarse-grain zone.
Janke: Grain Refining of Structural Steels by Dispersion of Fine Oxide Particles.

If it is assumed that nucleation only occurs at grain boundaries, then a given number of nuclei per length of grain boundary in a fine grained material will lead to more homogeneous recrystallisation than the same number in a coarse grained material.
Therefore, a large initial grain size provides fewer nucleation sites due to the reduction in grain boundary area per unit volume.
Note that after a reduction of 50%, the original fine-grained (A) material gave an appreciably finer grain size after recrystallisation than the original coarse-grained (C) material.
However, after a 70% reduction, the grain size after recrystallisation was similar regardless of different initial grain size.
The recrystallised grain size decreased markedly with increasing deformation and decreasing initial grain size.

The intergranular fracture mode of TE indicates a weakening of the grain boundaries.
Existing studies have suggested that the segregation of residual elements, such as phosphorus, stannum, antimony, and arsenic, at the prior austenite grain boundaries is responsible for the embrittlement, a finding verified by a number of Auger electron spectroscopy (AES) studies [4,5].
Small carbide particles situated at the prior austenite grain boundaries and martensitic lath boundaries can be observed.
The number of these particles per unit area is greatest at this tempering temperature.
These small particles situated at the grain boundaries can be identified as cementite.

When the carbon content increases from 0.27% to 0.35%, the number of the spherical VN or V(C,N) increases obviously and the size of it varies from 20~100nm to 45~105nm, while the number of flake VC and fibrous VC decreases significantly and the length of fibrous VC shortens from several micrometers to nanometer size.
The effective precipitation of V(C, N) in austenite may induce intragranular ferrite and fine ferrite grain [1,2].
With the increase of carbon content, the number of spherical precipitates obviously increases, and the size of it becomes larger.
The main useness of them is precipitation strength, which is the most important way of strength only second to fine-grain.
Furthermore, the smaller size and the more number of precipitate can get bigger strength effect.

Therefore, the stored energy density of the grain which the site i in the MC-Potts model locates in, namely the stored energy per unit volume, Hi can be express as [10] (1) where Hm is the average stored energy density in MC computing domain; di, dm are the equivalent diameter of the grain which site i locates in and the average equivalent diameter of grains in the computing domain respectively; K is the constant used in describing the position of site i, which locates on grain-boundaries,and in grains,; si, sj are the orientation numbers of the grains which adjacent site i and j locate in respectively; is the Kronecker function related with the grain orientation number, in grains,and, in grain boundaries,and; the number of sites j adjacent to site i.
Nucleus numbers.
The site space dMC=1μm, the average equivalent size of initial grains d0=25μm and the total orientation numbers Q=180 were set up.
When ending the second MCS (2MCS) computing in △t2, the number of DRX grains is not only more than ending 1MCS computing in △t2, but also the DRX grains generated in 1MCS grow up in varying degrees, and the boundaries of growing grains majorly migrate towards the high-energy deformed grains (see Fig.4d).
The recrystallized grains generated in △t1 are very small, and their numbers also are very few.

This precipitates could avoid the grain growth during subsequent annealing treatments [6].
In this condition, the microstructure is essentially composed by equiaxed austenitic grains within stacks of thin martensite plates, annealing twins and a number of large precipitates.
These precipitates were located mainly at the triple junction and grain boundaries.
The deformed grains present some amount of stress induced martensite plates and shear bands.
Kaufman, Influence of grain austenite grain size on mechanical properties of stainless SMA.

A variety of models have been proposed to interpret this relation 1-5, and a number of experimental investigations have studied dislocation behavior in the vicinity of grain boundaries 6-10.
The grain boundary is indicated by arrow-heads.
As the indenter penetrated further, a large number of dislocations were emitted on the far side from the indenter tip (left and lower side on the micrograph) of the grain boundary into the adjacent grain.
Li: Petch relation and grain boundary sources.
(a) low-angle grain boundary and (b) high-angle grain boundary.