Search results

At 1100℃, the average grain size is about 17µm, and most grains are in a uniform size, while a few large grains with irregular shape are also identified.
When the temperature is at 1160℃, the grains are uniform and the average grain size is about 28µm.
At 1180℃, the average grain size is further coarsened.
Fig. 6b is the microstructure at the strain of 40%, the number of large grains reduces and the sizes are more uniform.
The grain size reduces during the process.

Recently a number of researchers focused on the combination of ECAP with an appropriate post-ECAE heat treatment in order to regain the ductility [10-17].
The average grain size of the T4 condition is shown in Figure 5a is ~5 µm.
This suggests that the formation of a truly homogeneous ultrafine-grained microstructure has not been completed.
Nevertheless, ultrafine grains with an average size of ~ 300 nm are formed in some regions.
ECA-processing of the naturally aged condition above 220°C does not necessitate BP and yields a continuous decrease of strength with increasing extrusion numbers.

The properties of welded joint will been improved by these fine crystal grain.
Following the increasing of magnetic field current, the numbers of α-Mg are increasing and display as equiaxed grain, the β-Al12 Mg17 are diffusion distribution at the grain boundary of α-Mg, showen in Fig.4 b).
The grain consist of coars α-Mg and series β-Al12 Mg17.
These broken crystal grains can refine grain and improve the properties of welded joint.
The properties of welded joint will been improved by these fine crystal grain.

By first taking the Grain boundary Discarded data Blank pixels (No data) Grain boundary Grain boundary Discarded data Discarded data Blank pixels (No data) Grain boundary Fig. 2 Schematic drawing of the averaging of crystal orientation map.
Therefore, the number of pixels was reduced to 90 × 93 with a step size of 7.5µm.
Most noticeable is the significant deformation heterogeneity at the microstructural level, either between grains or within individual grains.
It can be clearly seen that some grains have regions where the local strain exceeds 9% whilst other regions of grains show less than 1% strain.
Although peak strains often coincide with regions near a grain boundary, highly strained regions also seem to exist in the central regions of the grains.

However, regardless of the number of compression cycles, the centre of the sample looks undeformed.
In case of the samples deformed up to 4 hits, this zone is composed of large grains, which grain boundaries are mostly distinguishable.
With an increase in number of MAC cycles to 8, many parallel deformation bands appears in this zone.
The distinction between grain interiors and grain boundaries at zone of large plastic strains is almost impossible.
This clearly indicates the grain refinement process.

Due to the increased complexity of steel microstructures, when considering the application of available Hall-Petch type equations for yield strength prediction, a number of difficulties raises.
FATT which is the temperature at which the surface of a Charpy test piece has a 50% ductile appearance has been expressed for ferrite-pearlite through an equation that takes into account a number of contributions [[] K.J.
However, for more complex microstructures, this formulation faces a number of problems addressed by the authors recently [[] A.
Optical grain size was determined by MLI on specimens etched with Nital 2%.
Conclusions -The grain size determined by EBSD depends on the tolerance angle applied for grain boundary definition.

Each lattice site is assigned to a number, n which corresponds to the orientation of the grain in which it is embedded.
In present study, Monte Carlo simulation was performed on a triangular lattice of size 200×200 sites with periodic boundary conditions and the number of distinct grain orientations, Q was 2,000.
The initial grain orientations (Q=2,000 numbers) were defined as the Euler angles (g) after separating from the ODF for the cold rolled 5182 aluminum sheets without annealing to the individual grains and these were used to generate a set of 2,000 initial grain orientations for Monte Carlo simulation.
In this simulation, when one lattice site is selected in order to try the orientation change, if the lattice sites were the interior of grains, the orientation change was not tried, however, it was included in the number of trial, N.
As time passes, the recrystallized grains are growing and the deformed grains are shrinking.

In a twinning-layer film, a number of new grains also can be formed.
There are a number of new fine grains, when static recrystallization occurs.
Therefore, the number of the nucleation of recrystallization decreases and reduces the grains to becoming coarse and asymmetry.
Therefore, the number of nucleation of recrystallization increases with a long time to complete the re-crystallization process, and fine and uniform grains are received finally at low annealing temperature [3].
In addition, the existence of a large number of twinning grains lead to the increase of strength of magnesium alloy sheets.

Grains have been defined as regions surrounded by 5º misorientation boundaries with a minimum grain size of 2.5 mm.
· Grain Orientation Spread (GOS): This parameter is the average deviation between the orientation of each point in the grain and the average orientation of the grain
As holding time increases, the distributions become narrower, with a significant increase in the number of grains with low GOS values (<2.5º), which can be associated with recrystallized grains.
In all cases a high number of grains with GAM values lower than 0.5º is observed.
The number and size of recrystallized grains increases with holding time (t = 100 and 3000 s).

As the annealing temperature increased to 275℃, as shown in Fig. 2(b) and Fig. 3(b), the number of recrystallization grains and their size increased obviously, but the microstructure was still dominated by the recovery microstructure.
Moreover, the number of recrystallization grains and the average grain size of Al-Mg-Zr alloy were smaller than those of Al-Mg alloy.
With the increase of annealing temperature, the number of recrystallized grains in the alloy increased inappreciably, even annealed at 575℃, so the recrystallization finish temperature of the Al-Mg-Sc-Zr alloy was difficult to determine (see in Table Fig. 4).
In the NZ (Fig. 7a4-c4), the grain structure of the three alloys were all fine equiaxial grain, and the average grain size of Al-Mg-Sc-Zr alloy was about 2~3μm, which are much lower than that of Al-Mg and Al-Mg-Sc-Zr alloy (about 5~7μm).
Combined addition of trace Sc and Zr in Al-Mg alloy, a large number of uniformly distributed Al3(Sc,Zr) nanoparticles formed, significantly reducing the width of HAZ, weakening the recrystallization softening effect.