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They significantly delay the austenite grain coarsening temperature, refine grains and prevent the abnormal growth of austenite grains.
They affect austenite grain growth significantly.
The grain coarsening temperature is 1100°C.
These second-phase particles pin austenite grain boundary and effectively prevent austenite grain growing in heating process.
That large grains swallowed small grains leaded to the number of grain boundaries are reduced and grains increased.

Within the elongated grains, a lot of low angle grain boundaries (LAGBs) were presented.
The grain refinement by such low strain was not significant: the width of elongated grains were about 40µm, although a number of equiaxed grains and subgrains were also observed.
A large amount of low angle grain boundaries (LAGBs) separates the large grains into lots of subgrains.
SP is an effective method for grain refinement as shown above.
By applying SP to as-rolled Al-Mg-Li alloy whose initial grain size was ~92µm in normal direction of sheet and ~252µm in rolling direction, a micrometer order grain structure with well-defined grain boundary was obtained.

Although a complete characterization of the grain boundary remains as a complex problem, since both grain boundary crystallography and boundary plane are necessary, the use of geometrical criteria for grain boundary classification has proved useful for technological development.
Nevertheless, a number of works[14,15] have shown the relation between dislocation and CSL boundaries, attesting for its specialty.
In this sense, grain boundary engineering becomes the search for different ways of altering the crystallographic nature of grain boundaries.
The possible ways through which the crystallography of a grain boundary may be altered are[16]: twining, grain growth, grain rotation, local lattice rotations, rotation and recovery of the grain boundary.
It is interesiting to notice that random grain boundaries has almost completely disappeared from neighbouring grains.

According to different experimental data the grain boundary diffusion the triple product (P) can change in opposite directions after alloying.
The grain boundaries in polycrystals are less studied objects.
The situation became more difficult if we speak about grain boundary diffusion (GBD).
One can find a number of results, demonstrated the depletion of the GBD by alloying.
Increasing of K value increases the number of Cu atoms participated in atomic complexes formation and excluded from the diffusion process.

Tensile Properties and Fatigue strength of Ultrafine Grained Pure Copper M.
Oxygen-free copper was processed by equal channel angular pressing with different numbers of ECAP process cycles, NP.
Here, the terms 1P, 4P and 8P mean the materials processed with the number of ECAP process cycles NP = 1, 4 and 8, respectively.
After the 8th pressing (c), no change in grain size was recognized, however the GB (grain boundary) contours appear to recover their sharpness.
The high HF values in UFG copper after formation of exiaxed grains indicated that the existence of non-equilibrium grain boundaries (N-E GBs) [2].

Next, these lamellas are subdivided by transverse LABs into sub-grains and/or (sub)grains bounded partly by LABs and partly by HABs (Fig. 2a).
However, certain grain orientations are resistant to CDRX, and large remnants of initial grains remain (Fig. 2b).
The size of the grains and (sub)grains remained nearly unchanged.
The number of dislocations emitted by sources was significantly higher than the number of dislocations consumed for the formation of LABs with misorientation less than 2º.
In this stage, the number of lattice dislocations accumulated by deformation-induced boundaries exceeds the number of dislocations stored within the interiors of the round crystallites.

In each element of that grid, the average impact velocity of all impacts is calculated, as well as the impact number and the maximal velocity (see also Fig. 5).
If we consider now the impact numbers, we can note that as one gets closer to the borders, the number of impacts increases (Figure 6).
Constitutive model for ultra-fine grained materials The third step consists of using the above results in order to predict the grain refinement.
In the first step, by simulating multiple impacts, statistical studies for impact number and velocity have been performed.
It could be noted that the impact velocity is higher in the centre of the sample and the number of impacts increases near the borders.

Annealed pure copper was subjected to equal-channel angular pressing (ECAP) by route Bc for different passes number.
Depending on the number of ECAP passes or collected true strain the microstructure parameters such as grain size, dislocation density and angle of grain boundaries are different [9].
Depending on ECAP passes number and therefore formed grain sizes, the specimens were classified as follow: N1 -CG, annealed; N2 - 4 ECAP passes by Bc route; N3 - 8 passes; N4 - after 10 passes.
Investigations established that during HCV deformation at stabile stress amplitude the grain size had not changed in dimensions as the cycles number is limited up to 20-30 as maximal.
During HCV deformation the dislocation density decreases and depends on cycle's number, amplitude and frequency.

Systematics of Grain Boundary Diffusion and Solute Segregation in Copper Poly- and Bicrystals Sergiy Divinski Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany divin@uni-muenster.de Keywords: Copper, grain boundary diffusion, grain boundary segregation.
The results on grain boundary diffusion and segregation are analysed in relation to the solute - solvent binding and solute - vacancy interaction in the bulk and in the grain boundaries.
Recently, a large number of such measurements were carried out with several representative solutes in the same high-purity polycrystalline copper.
With increasing group number the solute diffusivity P is increased.
McLean: Grain Boundaries in Metals, (Clarendon Press, Oxford, 1957).

Most of the grains are micro-broken during grinding, and they have high-usage [3].
A large number of studies on abrasion mechanism have shown that single diamond grit's failure has a close relationship with its load.
The normal abrasion mechanism of diamond grain has been found through the comparison between the single grain tangential load during grinding and the single diamond grain's shearing failure-load of the samples.
Moreover, it can be seen that few of grains were pulled-out or broken-off.
And few of grains were pulled-out or broken-off during grinding process.