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With removal from the active zone of deformation the grain size increases, and microhardness decreases.
At the same time these alloys possess a number of advantages the major of which is an opened single-phase α-area along with an economy of cobalt.
In the top part of the samples, near to fixed head, the of grain size was maximum and in the middle part it has an average value.
The fraction of special grain boundaries sharply decreased and the fraction of low angle boundaries considerably rose.
It was shown that application of the method of complex loading allows obtaining gradient microstructure with minimum grain size near to mobile head and a constant increase in a grain size along the vertical axis of the sample. 2.

C in Fig.1c) is still rod-like distribution along the grain boundary, has not changed on the morphology during aging.
As shown in Fig.1d, after artificial aging, a large number of precipitates were precipitated in the crystals (shown in black and gray hue).
In this paper, on the one hand, a large number of precipitates would pin partial dislocations during aging treatment, but in the process of quenching and aging could produce a large number of newly dislocations and interfaces, which "make up" the dislocation damping performance loss caused by precipitate pinning.
Although the grain growth will occur in the aging process, but the modification additions can hinder the grain growth.
However, adding Sb can refine grains and hinder the grain growth and the reduce of equiaxed degrees during aging, which conducive to the non-elastic viscous movement of grain interface.

The individual grain orientation was measured by EBSD in a FEG-SEM.
A great number of needle-shaped δ phase distributed in the grain boundaries disappeared after solution treatment.
With the increasing of hot deformed temperature, the dynamic recrystallized grains become more uniform and the grain size increased.
The dynamic recrystallized grains are finer than the original ones.
Fig. 4 (c) shows the typical neck-structure of superalloys which there are many fine recrystallized grains around the big grains.

As the dotted box shown in the Fig.2, it can be found that many regular grains turned into elongated grain, and some grains were even cut into several parts.
Furthermore the number of small equiaxed grains began to multiply, and there were some relatively large recrystallized grains formed in the matrix.
This was the consequence of high-angle grain boundaries devouring small-angle grain boundaries.
For the Al-wt.5%Si-Al2O3 composites, it could be similarly caught that a large number of equiaxed grains had been formed inside the sample after heat treatment of 500°C for 1h, and the grain size was also basically close to the original grain.
However, with temperature increasing, the migrated ability of grain boundary improved greatly, so the recrystallized grains in the region with relatively low pinning effect can also grow to large grain through a mechanism of large angle grain boundary bypassing or crossing particles to swallow the small recrystallized grains around, as shown in Fig.3 (d) and (e).

The grain size is 24~28μm.
The grains are not homogeneous, and the average grain size is about 10 μm.
The dislocation pile-up consists of a large number of dislocations which are intensive in the front and sparse at the back.
Furthermore, a large number of dimples, which present echelonment along the depth direction, appear in the position of fracture.
In fact, the microstructure of the tested steel becomes more uniform and the number of dislocations decreases after solution treatment.

The fine-grained structure guarantees excellent plastic properties as well as high impact toughness.
These steels were conventionally numbered: 225, 227 and 228 and their chemical compositions are presented in Table 4.
It is possible to notice small numbers of the laminated ferrite precipitated at the boarders of the primary austenite grains in case of lower temperatures of the end of the deformation (780 and 760oC) a small banding of the structure.
Innumerous precipitations of the carbides inside of the ferrite grains are also observed.
When cooling from the temperature of 800oC, grained ferrite with the precipitations of carbides was obtained, a small number of needle-like ferrite and the bainite-martensite islands (Fig. 4).

JIS G 0551 requires the magnification which can catch the number of grains more than 50 in the intercept method, but we counted it with magnification ×300 in order to measure the PAG sizes in both areas.
We counted the number of grains which were intercepted by the test lines from a microscope image (magnification ×300).
(1) where L is an average grain size [µm], L is a length of the test line [µm] and N is the number of grains intercepted a unit length.
Prior austenite grains.
Prior austenite grain boundaries were observed in both areas.

The modification has obvious refining effect on primary silicon and eutectic silicon grains, electromagnetic stirring has refining effect on primary silicon grains, and eutectic silicon grains appear coarsening phenomenon.
Thus, eutectic silicon grains change from coarse needle flake to fine dot shape.
It can be seen from the figure that with the increase of the constant temperature time, the primary silicon grains in the aluminum silicon alloy increase and the number decreases.
Electromagnetic stirring can refine and passivate the primary silicon grains, but coarsen the eutectic silicon grains.
Räbiger, et al., Grain size control in Al–Si alloys by grain refinement and electromagnetic stirring, J.

It should be pointed out that there is a theoretical restriction on the possible time-step (Dt) and mesh-size (Dy) combinations giving a Fourier number of Fo in order to achieve a stable solution, i.e., Fo=∆tλΔy2ρCp<0.5 (9) The heat transfer problem can be solved using an explicit finite difference method [5].
The effective austenite grain size for each grain component can be estimated via the law of mixtures using the recrystallized and un-recrystallized grain sizes together with the fraction of each component.
A summary regarding the average grain size for the deformed and recrystallized grains average strain for the deformed grain are listed as well.
It can be seen after pass 4 that the tendency for the presence of partial recrystallization is clear and grain structure is a mixture of deformed and fully recrystallized austenite grains.
Average grain size for deformed grains = 12.990 µm Average grain size for recrystallized grains = 14.45 µm Average grain size = 14.410 µm Average strain for deformed grains = 0.050 Average strain = 0.001 Average grain size for deformed grains = 14.420 µm Average grain size for recrystallized grains = 12.17 µm Average grain size = 13.370 µm Average strain for deformed grains = 0.064 Average strain = 0.034 Average grain size for deformed grains = 13.280 µm Average grain size for recrystallized grains = 8.290 µm Average grain size = 12.510 µm Average strain for deformed grains = 0.085 Average strain = 0.072 Average grain size for deformed grains = 12.470 µm Average grain size for recrystallized grains = 7.650 µm Average grain size = 12.100 µm Average strain for deformed grains = 0.091 Average strain = 0.084 Fig. 5 Predicted Grain size hierarchy for passes 4, 5, 6 and 7 References [1] C.M.

It was observed that more number of grains (~75%) lies between 40-60 µm sizes in case of LAT971C.
The high number fraction of lower grain size (<30 µm) is increased in case of LAT971R.
This confirms the presence of more number of strain free grains, which is attributed to the dynamic recrystallization (DRX) in α-phase as a result of homogenization and hot rolling at ~573K [12].
This was estimated by providing a criterion for the grain boundary (misorientation exceeding 15o) and then isolating the grains.
For a given grain, the average misorientation was calculated between all neighboring data points in the grain.