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Previously, the authors reported the low misorientation boundaries decreased as increasing the number of ECAE pass and the degree of extra-hardening varied with the characteristic of grain boundary distributions [2].
Figure 2 shows the relationship between the grain boundary fractions, average misorientations and the number of ECAE passes.
As a result, the dislocation density decreased with increasing the number of ECAE passes as shown in Figure 3.
The relationship between the grain boundary fractions, average misorientations and the number of ECAE passes.
Fig. 3.The relationship between the dislocation density and the number of ECAE pass.

The recrystallization grain sizes of the fibers annealed at different conditions were calculated by quantitative metallography using the equation (s is the sectional area of the fiber, and n is the number of the grains).
There are a large number of stripes on the surface of the fiber (Fig. 2(a)), which can be attributed to the bundle-drawing friction.
Grain coarsening accompanied by smoothing of the grain boundary takes place with the holding time increasing.
It has been reported [17] that a strong crystallographic texture can arise at least in part from a large number of grains of similar orientation leading to a greater number of low-angle boundaries.
After bundle drawn, a large number of stripes appear on the surface of the fiber.

One way for enhancing the strength is decreasing the grains size and reach ultrafine grains.
In recrystallized samples at high temperatures, grain boundaries were moved toward out for decreasing the number of grains.
In uncommon growth few of the grains become course and other grains are covered by these grains.
The grain size was 21.5 μm but grains grew and the grain size became 31 μm at 620oC and 49 μm at 635oC.
Grain sizes were measured by the grain size Eq. (3): D=1N4A/πN (3) where D is the grain size , A is the area of grains measured by the UTHSCSA Image tool softwear and N is the number of grains.

The initial workpieces were heated at 1150 °C for 5 minutes, resulting in a homogenous initial grain size of 200 µm which is assumed as the initial grain size for the first stage.
Different values of initial grain sizes are required to obtain the exponent of initial grain size, denoted as h in Eq. (1).
Measured grain sizes were averaged over a small measuring circle with diameter of 1000 µm.
Of course, employing the T-dependent Q and m increases the number of material constants to be determined through optimization and consumed time accordingly.
Optimized DRX constants including initial grain size exponent, strain exponent, strain rate exponent and dynamic recrystallization activation energy are acquired iteratively, minimizing the objective function of errors between target grain sizes and predicted grain sizes at the sampled points.

Much of the work has been on the development of ultrafine grained steels.
Therefore, ultrafine grained steels are expected to have higher reduction in area, compared to conventional grain size ferrite - pearlite steels.
The aim of the study was to evaluate the strength and reduction in area balance of these ultrafine grained steels and to verify good formability of ultrafine grained steels.
Although some sub grains and ferrite grains elongated in the rolling direction have been retained, a large number of equiaxed ultrafine ferrite grains surrounded by high angle grain boundaries were observed.
However, among the grain boundaries with low angle grain boundaries of 5°εθε1.5°, high angle grain boundaries of θε15°and middle angle grain boundaries of 15°εθε5°each account for approximately 35% of total grain boundary length.

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.

Grain boundaries can therefore more easily break free from the particles than in purely two-dimensional systems, resulting in fewer grain boundary–particle intersections and a larger final grain size.
The dispersively distributed second phase particles in alloy inhibit the matrix grains growth so as to refine grains.[1-3] Experiences have proved that fine grain strengthening is the only way improving the toughness meanwhile improving strength.
Second phase particle generation technology During the initial stage of simulation, particles are generated according to the second phase particle’s shape, radius r and volume fraction f (area fraction f in 2D cellular automata model), orientation number value of 0 to distinguish from normal grain, and in the process the value keeps constant.
With a square particle as an example, its area can be obtained as long as its sides are determined, then can calculate total number of particles.
(2) Calculating the second phase particle numbers according to f : (4) Where, Stotal for total cellular area

The elongated grains are observed in the parallel extrusion direction and a grain size of ~ 200 µm.
The variation of mechanical properties of 3003 Al alloy with the number of pressings; (a) yield and (b) tensile strength, (c) elongation.
Fig. 3 shows the variation of the mechanical properties with the number of ECA pressing using three routes.
After one pass, the yield and tensile strength increased with increasing number of ECA pressings and work hardening is observed.
Tensile and yield strength for Al billet produced by route A and BC was improved with increasing number of ECA pressings while those for Al billet produced by route C was greatly not changed with number of ECA pressings after one pass.

The dynamic evolution of grain growth in the process of aluminum casting and the impact of different casting conditions on the grain growth were simulated by using the Cellular Automation(CA) method in this paper.
A computer was used to simulate microstructure formation of aluminum in the grain scale.
Based on the above considerations, in this paper, the CA method was used to simulate the grain growth in the solidification process of aluminum casting and the effect of the process parameters on grain growth.
(8) As, a unitary quadratic equation about can be got as below: (9) Where: is the diffusion coefficient of solute, , is the growth velocity of dendrite tip, is the slope of liquidus, is the compositionally gradient of interface, is the function of Peclet number, is the average temperature gradient, is the stability constant, ,is the Gibbs-Thomson coefficient, is the ingredients undercooling, is the curvature undercooling, is the thermal undercooling, is the kinetics undercooling, is the solute partition coefficient, is surface energy,is volume melting entropy, is the Peclet number of solute, is the Ivantsov function of Peclet number, ,, is the initial concentration of the alloy, is the solute partition coefficient,is the growing radius of dendrite tip.
The dynamic growth of grain shows as Fig.2.

Formation of High-Angle Grain Boundaries in Iron upon Cold Deformation by Equal-Channel Angular Pressing S.
The basic ECA pressing parameters governing the processes of the structure formation include temperature, number of passes, pressure, angle between channels, and pressing route.
The grain size is 200-500 nm.
Distribution of misorientations for various routes and number of passes in ECA pressing at room temperature (EBSD analysis): a.
Route Bc, N=4. 10 20 30 40 50 60 0,0 0,1 0,2 0,3 0,4 Number Fraction Misorientation Angle [degrees] 10 20 30 40 50 60 0,0 0,1 0,2 0,3 0,4 0,5 0,6 Misorientation Angle [degrees] Number Fraction а b c d Summary The examination by the methods of transmission and scanning electron microscopy and EBSD analysis revealed the formation of partially submicrocrystalline structure with a grain size of 200500 nm in the α-Fe upon cold ECA pressing to ε ≅ 4.5.