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For AZ61, the elongation increased with the increase of ECAE pass number and the decrease of grain size.
However, the elongation of AZ91 with more second phase particles decreased with the increase of ECAE pass number and the decrease of grain size.
Introduction Grain refinement is an important practice to improve the mechanical properties of magnesium alloy, where equal channel angular extrusion (ECAE) provides a technique for producing ultra-fine grain sizes in the submicrometer or nanometer range in bulk materials [1, 2].
For the AZ31 and AZ61 Mg alloy by ECAE, the elongation increased but the strength decreased with pass number increasing, which are similar with the study results in Jin's[6] and Kim's work [4], which were due to the grain refinement and texture evolution in these alloy.
However, for the AZ91 (a) (c) (b) (c) (b) (a) Mg alloy, the elongation decreased with the pass number increasing.

akrphaneesh@gmail.com, banirudh_bhat86@yahoo.com, cquasar66@gmail.com, dktkashyap@yahoo.com Keywords: Particle size; Average grain size; Largest grain size; Zener limit; Grain size distribution; Particle fraction on grain boundaries.
Different grain growth parameters such as mean grain size, largest grain size, fraction of second phase particles lying on grain boundaries, etc., were computed for the pinned microstructures.
Simulation studies in grain growth was pioneered by Srolovitz et al and others [1 - 3] who investigated grain growth kinetics, grain size distributions, the limiting grain size, among others, in both two-dimensional and three-dimensional crystals.
Since the effective number of particles pinning the grain boundaries decrease with increasing particle size for the same surface fraction, the Monte Carlo steps required to bring about stagnation is also more.
Sahni, Computer simulation of grain growth-I.

The recrystallizing grains in these initial microstructures have a lognormal distribution and the recrystallized number density (grains/mm 2) decreased during annealing, with the initial microstructures affecting the degree of this decrease in number density.
The PF microstructures consists of polygonal ferrite (average grain size ~ 40 µm) decomposed from coarse austenite (grain size ~300 μm), with pearlite distributed at the ferrite grain boundaries.
There are a number of factors influencing the rate of recrystallization, such as original grain size, deformation microstructure, solutes, degree of cold rolling reduction and annealing temperature [8].
At the early stages of recrystallization, a large number of fine grains are generated.
While the grain size distribution remains log normal throughout recrystallization for all samples, there was a general decrease in the area density of recrystallized grains (number of recrystallized grains per mm2) (Fig. 5).

Microstructure was quite homogeneous and polygonal grains were observed.
Mean grain size was 0.8 µm.
In this case mean grain size was 1.7 µm, while in Fig. 3b the microstructure of the sample annealed at 700°C x 3 min showed an inhomogeneous microstructure with some coarse grains, indicating that abnormal grain growth occurred.
Increasing the number of passes the non recrystallization temperature decreases and during heating and warm rolling some microstructural changes occur.
Inside the elongated grains there are a lot of small grains with low boundary angles.

As one of severe plastic deformation processes, ECAP can improve materials’ mechanical properties by grain refinement [4, 5], and a large number of studies were carried out to identify it [6-8].
But at 300℃, the ɛave reduce by about 1/4, and it is not conductive to grain refinement.
The grain is elongated to be broken after one pass ECAP.
With the deformation goes on, the original grain and the big grain deform due to the dislocation caused by stress.
Because of the dynamic recrystallization, the grain is further refined.

An RVE must include a large number of the material’s micro-heterogeneities (e.g., grains, inclusions, voids).
Specific mechanisms of grain refinement are studied in a number of publications (see, for example, [14, 23]).
The above view explains a number of effects observed during simple shear, including the following: 1.
This can be done using either the yield stress YS or the Vickers hardness number (HV) of the specimen.
Fig. 7 shows the shape of the inclusion after a given number of shifts.

Ferrite Grain Refinement during Hot Rolling of Seamless Tubes R.
The composition of the steel was 0.2C, 1.44Mn, 0.24Si and 0.12Cr, all numbers in % weight.
The starting grain size for the torsion experiments were certainly higher than 100µm, as there was no pinning effect limiting grain growth during heating.
The grain size of torsion sample quenched at a point simulating withdrawal of the tube from TF shows that the austenite grain size leaving TF is about the same size as for the grain which left CMM.
This in turns determines final ferrite grain sizes bring refinement of these grains by a factor of almost 2, that is, from 20.8 to 12.4µm.

Higher microhardness numbers were generally found near the casting surface, at the corners and along the segregation band.
The majority of lower hardness numbers was found at the core region.
A few very low hardness number points, in the range 30~45 Hv, were also found in the core region.
Many of the highest hardness number concentrate at one of the corners in Fig. 1-a.
Dendritic grains appeared dispersed in the surface and corner regions as well, although they were much fewer in number than at the core.

In addition, an inclusion of length scale of grain to simulate the SIMT behavior is very important and the studies which consider the effect of numbers of grains and representative grain morphologies effectively are still developing.
The actual TRIP steel is a polycrystalline material which consist an aggregate of a number of grains and the martensitic content varies from grain to grain.
A set of Voronoi tessellation with the numbers of crystal grains of 6 and 20 is chosen as shown in Fig. 2 (a) and (b).
Here, the total number of variant systems is 24 [14].
Next, Fig. 5 shows the distribution of phase for the case of 20 grains with Pattern 2 in order to investigate the effect of numbers of grain on the SIMT behavior.

Grain refinement of Zn-25Al alloy through the addition of Zn-6Ti master alloy Z.Q.
The mechanism for the grain refinement is discussed based on the SEM observation of TiAl3-xZnx particles at the center of α-Al grain in Zn-25Al alloy.
Recently, grain refiners, e.g.
In this paper, we will briefly report the grain refinement of Zn-25wt.
The α-Al grains in the original Zn-25Al alloys (without the addition of grain refiner) solidified from 570℃ present complex dendritic structure which contains a number of primary and secondary arms, which exceeds 300μm and 70μm in length, respectively(Fig.4(a)).