Search results

Thus, at average grain size of materials below ~100 nm, the plastic deformation may occur due to the grain boundary sliding (GBS) mechanism which reduces the grain size strengthening effect.
The average grain size is about 9 nm.
Commonly, atoms in Al GBs have a coordination number different from 12 of an ideal fcc lattice.
Therefore in order to create the computational cell for the NC Al-Co and Al-Mg alloys with the GB segregations, the Al atoms with the coordination number equal to 11 or 10 are replaced by the corresponding alloying atoms.
This process results in a grain growth.

The peak positions shifted to lower temperature as the number of ARB cycles increased.
The stored energy continued to increase with the increasing number of ARB cycles.
The area fraction of cube grains increased with the increasing the number of ARB cycles.
Above the number of 4 cycles of the ARB process, the recrystallization is mainly caused by the preferential growth of cube grains and induces the development of cube texture.
The cube texture depends on number of ARB cycles.

Globular δ phase precipitation precedes that of the plate-like δ phase, forming at grain boundary first and later in grain.
The δ phase restricts the growth of recrystallized grain and accordingly microstructure with fine grains is carried out[3, 4].
The initial grain size was about ASTM 11 mixed with uneven big grains, which is unfavorable for industry application.
Fig. 4(b) illustrates that high density of globular δ phase disperses in the matrix with only a small number of plate-like ones at grain boundary.
Conclusion (1) Globular δ phase first occurred at grain boundary and later within grain when the alloy was holding at 910℃.

However, very recent advances in the processing of theoretically-dense metals with submicrometer grain sizes have provided the opportunity to extend the understanding of flow behavior to include materials where the grains are exceptionally small.
Following ECAP, the mean linear intercept grain size was L = 0.3 µm corresponding to a spatial grain size of d = 1.74 × 0.3 ≈ 0.5 µm.
It is apparent from Fig. 1(b) that the maximum elongation occurs at a faster strain rate after pressing through 8 passes and this is due to the increasing fraction of high-angle grain boundaries with increasing numbers of passes in ECAP [15].
Both of these alloys were fabricated from high purity materials and the grain sizes prior to ECAP were ~200 µm in the Al-Mg-Sc alloy and an exceptionally coarse grain size of ~10 mm in the Al-Sc alloy.
Horita, in: Ultrafine Grained Materials IV, edited by Y.T.

For D0 = 22 µm, grain fragmentation takes place due to frequent formation of kink bands initially at corrugated grain boundaries and then in grain interiors in low strain, followed by full development of new fine grains in high strain.
Then new grains are formed in necklace along the boundaries of coarse original grains, followed by their development into the grain interiors.
Fig. 4 shows effect of initial grain size on the volume fraction of new grains (Xv), the recrystallized grain size (D) and the average misorientation (θav) for the Mg alloy deformed at 573K.
Kink bands followed by new grains are scarcely developed in the twinned grain interiors for the coarser grain sample.
The misorientation and the number of boundaries of kink band rapidly increase with deformation, finally followed by the in-situ evolution of new grains with high angle boundaries at high strain

AGG-grains are not equiaxed.
The same procedure was adopted for 30 nuclei giving a total number of 515 misorientations.
In average, over 10,000 grains were counted for calculations.
Penelle, Influence of the Goss grain environment during secondary recrystallisation of conventional grain oriented Fe–3%Si steels, Scripta Mater. 47 (2002) 725-730
Morawiec, On abnormal growth of Goss grains in grain-oriented silicon steel, Scripta Mater. 64 (2011) 466-469

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.

Large Nb-rich particles may enhance sub-grain structure development (formation of twins and deformation bands), which in steels may lead to an increase in the number of ferrite nucleation sites and ferrite grain refinement [10, 11].
After deformation the observed grain size was almost similar in all the three alloys, although the NbC number density varied significantly.
In alloy M, due to a maximum of the NbC number density, the recrystallisation proceeded at a lower rate but the grain growth was also significantly retarded.
During holding after deformation the grain growth took place, which was accompanied by the particle coarsening and a decrease in the particle number density.
The grain growth was similar in alloys M and H, although the NbC number density after deformation was higher in alloy M than that in alloy H.

Experiment and conditions Grain-arranged diamond wheel.
Many grains on the wheel surface have been traced using the microscope system and almost all the grains remained by 500th pass, total removal depth of 10mm.
Fig. 5(a) shows the grains before grinding under vertical lighting.
Fig. 9 shows a change of normal and tangential grinding forces, FBnB, FBtB, and Fig. 10 shows a variation of surface roughness, RByB, with the number of grinding passes, n.
Therefore, the less grain size and the more grain density are recommended for the stable production of mirror surfaces without grinding burn.

Moreover, the cases of the as-received sheet with smaller grains had smoother surface textures than those of the annealed sheets with larger grains.
In a micro metal forming process, it may be only a small number of grains directly involved in deformation.
Experiments Grain Size.
The cases of the as-received sheet with smaller grains had smoother surface textures than those of the annealed sheets with larger grains.
Moreover, the cases of the as-received sheet with smaller grains had smoother surface textures than those of the annealed sheets with larger grains.