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It is therefore necessary to evaluate the Schmid value, m of all potential slip systems in order determine the actual number of active slip systems.
As a consequence, it is very difficult to determine the number of activated slip systems in grains with this or similar orientations.
It is clear that the slip behaviour depends upon the initial crystallographic orientation, i.e. the number slip systems activated is very heterogeneous through the profile thickness.
Fig. 6: Rotation path of the tensile direction during increasing deformation. a) Grain A. b) Grain B c) Grain C d) Grain D and e) Grain E.
• The number of slip systems activated during deformation is strongly dependent upon the initial orientation and is therefore very heterogeneous through the microstructure

A good correlation between the number of adjacent grains (AGA), and therefore the grain shape (granoblastic and xenoblastic), and the durability, was confirmed in a 2006 study [5].
Three of them are characterised by a polygonal grain shape: GI, PS, SG, PS and SG, at difference of GI have a higher grain size and a seriate structure.
AGA Method The Adjacent Grain Analysis (AGA) was carried out in accordance with the EN 16306 Annex C (2013) by means of the free software ImageJ in order to calculate the number of adjacent grains (AG) around median-sized grains.
Afterwards, at least 50 median sized grains were chosen and a manual count of the number of their adjacent grains was carried out.
These differences may be related to the marble grain size.

A study has been carried out on the evolution of microstructure, grain boundary character and mechanical properties in a Twinning Induced Plasticity steel heavily cold rolled and subsequently annealed.The cold rolled mcrostructures showed fine lamellar boundaries with many shear bands.With progress of annealing, numerous numbers of recrystallized grains were generated.The fully recrystallized steel showed equi-axed nanocrystalline grains with a mean grain size of 400 nm that enhanced the yield strength significantly while retaining tensile ductility.
However, there is no information available about the effect of ultra grain refinement (grain size < 1 mm) on the tensile properties and their deformation behaviour.
Nanocrystalline grains are surrounded by high angle grain boundaries (HAGB) and many ∑3 annealing twin boundaries are involved in the microstructure.The mean grain size calculated including twin boundaries was 400 nm.
In summary, ultra grain refinement of the TWIP steel was examined.
In the fully recrystallized condition, equi-axed nanocrystalline grains with mean grain size of 400 nm was achieved by cold rolling and subsequent annealing.

Grain Boundary Engineering for Intergranular Corrosion Resistant Austenitic Stainless Steel H.
Recent studies on grain boundary structure have revealed that the sensitization depends strongly on grain boundary character and atomic structure, and that low energy grain boundaries such as CSL boundaries have strong resistance to intergranular corrosion [1-3].
The concept of ‘grain boundary design and control’ [4] has been developed as GBE [5].
In this study, grain boundaries with ��29 were regarded as low-� CSL boundaries, and Brandon’s criterion [8] was adopted for the critical deviation in the grain boundary characterization [3,9].
A number of twins formed in the growing grains compensate grain-coarsening.

Both processing techniques, WP and CRA, leads to grain refinement and formation of the grain-subgrain structure of submicron scale in the steels.
Quasi-equiaxed grains with banded contrast are also observed in the structure of the WP-specimens because of formation of ε-phase plates in austenitic grains.
CRA-treatment produces the ultrafine-grained structure with a grain size of 210 nm in 321-type steel (Fig. 1d).
On the side-surfaces of hydrogen-precharged and broken samples, a large number of cracks formed in the fracture zone (Fig. 3f).
On the side surfaces of the samples, there is no large number of cracks (Fig. 4c), but on the fracture surfaces, a brittle 20 μm-zone with numerous secondary brittle cracks is observed (Fig. 4d).

Both in the two alloys, surface relief was formed at most grain boundaries by the stretching, while hydrogen evolution was observed at some grain boundaries.
A number of white particles were observed at some grain boundaries and slip lines of each specimen.
The larger the tensile deformation amount, the greater the number of grain boundaries with hydrogen evolution in Al-Mg specimens.
Both in the two alloys, surface relief was formed at most grain boundaries by the stretching, while hydrogen evolution was observed at some grain boundaries.
In a peak-aged Al-Zn-Mg alloy, precipitate free zones (PFZs) exist along grain boundaries and deform more easily than the interior of the grains [6] and also than the zones near the grain boundaries in the Al-Mg alloy that have larger numbers of solute atoms.

But grains grew up obviously after normalizing annealing at 850°C for 1h because the mobility of grain boundary is so good at elevated temperature that pinning effect of precipitates can’t prevent the migration of grain boundary.
At least 100 grains were randomly measured in each case and the average grain sizes were estimated.
(a) (c) (b) (f) (e) (d) Fig. 1 Microstructures of the coiled bands (a) 550°C/1h, (b) 550°C/2h, (c) 550°C/3h, (d) 650°C/1h, (e) 650°C/2h, (f) 650°C/3h Table 1 Average grain sizes and the dates of precipitates in the coiled bands Process Average grain size [μm] Precipitate Average size [nm] Number density* Volume fraction [%] 550°C/1h 20 124 3.9 0.047 550°C/2h 23 134 5.0 0.065 550°C/3h 24 138 4.7 0.070 650°C/1h 21 148 4.5 0.067 650°C/2h 24 118 6.6 0.070 650°C/3h 29 110 9.1 0.084 * The number density of precipitates represents the average number of precipitates in a view field.
Hence, grains coarse obviously, which suggests normalizing annealing is necessary in order to gain large grains.
After normalizing annealing at 850°C for 1h, grains grew up obviously owing to the good mobility of grain boundary at elevated temperature and the average grain sizes are more than 100μm.

There are a number of instances of ductile ultra fine-grained materials.
However, most of the limited number of studies of tensile ductility in nc elemental metals have revealed poor ductility.
Distributions of both number and volume fractions of grain sizes were presented.
The mode of the volume distribution was found to be much larger than that for the number distribution.
Ma, Ultrafine Grained Materials, ed.

IN THIS WAY A SIGNIFICANT REFINEMENT OF GRAIN IS ACHIEVED BY SEVERE PLASTIC DEFORMATION.
Grain size reached the value G4 according to the ASTM.
Grain size reached the value from G5 to G6 according to the ASTM.
As it can be seen from Fig.7a (200°C/15 min) in this case no grain refinement took place, while grain refinement shown in Fig.7b (400°C/15 min) is bigger, than in the samples without heat treatment.
Grain size reached the value G8 according to the ASTM.

The growth of Goss grains is facilitated when the normal growth of other grains is suppressed.
In Fig. 1(b), an island grain is observed inside one large grain and a small number of finer grains are present in the boundary of the larger grains (noted with Y).
(a) (b) Fig. 1 SEM images of 900°C 30 min RH annealed sample (a) abnormal growth large grain (b) a large grain with an island grain inside it and some finer grains present at the boundary of large grains.
For grains ~ < 100 µm in size, these grains readily grow during the first 5 min of annealing for both the RH and SH samples.
As the annealing time is prolonged, the growth of Goss grains in the SH samples is limited as these grains appear to have already reached saturation.