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The grain was refined after ECAE, the finest grain size can reach 2.5 mµ (Table 2, Figure4-(c)).
However, further refining can't be achieved even when the numbers of extrusion are increased because the recrystallization has finished.
The above data and associated argument indicate that fine or extremely fine grain by ECAE is not solely dependent on extrusion number of passes.
The average grain size is about 150 mµ
Table 2 Effect of ECAE process on mechanical properties of AZ31D Extrusion condition and the grain size Test conditions Tensile test results ECAE temperature(K) Pass number Grain size( mµ ) Test temperature(°C) Strain rate(1/S) Elongation (%) Peak stress (MPa) *** 0 100-150 350 0.0002 89 22.4 *** 0 100-150 400 0.0002 120 45.8 *** 0 100-150 450 0.0002 90 20.1 523 1 10 380 0.001 125 47 523 2 8.5 400 0.001 260 33 523 3 5 400 0.001 95 34.1 523 4 2.5 400 0.0002 160 26.4 573 1 20 400 0.001 280 35.1 573 2 12.5 400 0.001 240 34.7 573 3 8 360 0.001 160 35.2 573 4 5 380 0.001 350 30 623 1 20-50 400 0.001 210 31.1 623 2 20-50 400 0.001 250 32.6 623 3 20-50 400 0.001 260 35.5 673 1 40 400 0.001 125 34.2 673 1 40 400 0.001 160 32.1 � �� �� �� �� ��� ��� ��� ��� � � � � � � Number of Extrusion Pass Average Grain Size(µm) ���� ���� ���� ���� Figure7 The average grain size after ECAE Figure 7 shows the change of the

The limited number of active deformation systems in hexagonal close packed (HCP) structure of Mg alloy lead to their poor formability at room temperature, which restricts the application of wrought magnesium alloys.
It can be noted that Al2Ca intermetallics locate in the grain boundary in slabby shape with reticulation structure for the as-cast Mg-11Al2Ca master alloys in the Fig. 3(a), whereas large number of Al2Ca phases are well-distributed in a particle or rod-shaped in the Mg matrix for as-extruded Mg-11Al2Ca master alloys in the Fig. 3(b).
Therefore, as-extruded master alloys are employed to study grain refinement behavior in this study, which would expect to have a better grain refining efficiency.
When adding a small amount of master alloys, grain will decrease in some degree, but the extent of grain size decreasing starts to slow down with further addition.
Grain size of AZ31 and AZ61 with different levels of the addition Mg-11Al2Ca The grain refinement mechanism of Al2Ca in Mg-Al based alloys.

A number of SEM images similar to that shown in Fig. 3 were used to evaluate the grain size of sintered compacts.
However, in this work, values of n=1(anomalous grain growth), n=3(solid-solution drag-controlled grain growth) or n=4 (pore drag-controlled grain growth) were not very acceptable.
Moreover, because no solid-solution drag-controlled grain growth (n=3) was expected[16-17], interface reaction-controlled grain growth (n=2) was the most probable grain growth mechanism.
Accordingly, the rate of grain growth is assumed to be proportional to the product of the grain boundary energy and grain boundary mobility.
The VC segregation layers at grain boundaries thermodynamically lowered the grain boundary energy, as indicated by the Gibbs adsorption isotherm, and reduced grain boundary mobility.

Measurement of plastic zone dimensions after different number of cycles of deformation show that plastic zone size increases during the first stage of cyclic deformation (until definite number of cycles are completed), and then remains unchanged.
The cracks form on slip bands inside grains or on grain boundaries.
Former austenite grain after 500 cycles. b.
However, after definite number of cycles further growth is ceased.
The maximal number of slip bands are oriented to the macrocrack at an angles 30-60o . 5.

However for applications such as YBCO HTS tapes the objective is to develop a grain structure with as many very low angle grain boundaries as possible.
Measurements of a large number of points within a grain of orientation g with a real mosaicity of χ results in a distribution of orientations with mean orientation g and spread > χ.
For each texture spread the misorientation at which 70% of the grains are connected decreases in an approximately linear fashion with increasing orientation noise (some deviation from linearity is seen due to the relatively small number of grains used in the simulations).
The reason for this is straightforward: because of the statistical nature of the orientation noise in EBSP data, the greater the number of measurements along a given grain boundary, the greater will be the chance that a measured misorientation along the boundary will be significantly lower than the real grain boundary misorientation.
Acknowledgements This work was supported by the National Natural Science Foundation of China under contract numbers 50231030 and 50371041.

The values of ASTM grain size numbers and percentage of nodularity across each specimen were tabulated in Table 1 and Table 2 respectively.
The tabulated results were plotted for different locations on the sample against the ASTM grain size number [Fig 3] and percentage of nodularity [Fig 4].
It was observed that ASTM grain size number and the percentage of globular grains has increased when the stirring speed was 400 rpm.
It was also observed that with the addition of grain modifier the ASTM number has increased as compared to original sample indicating that the grain size has reduced but the percentage of nodularity has increased.
ASTM grain size number for Sample 1 Nodularity% report for Sample 1 Fig 5 V.

The obtained results can be used to model grain growth in molecular dynamics studies.
Among others, two such mechanisms that involve grain boundaries are Strain hardening and Grain size hardening.
However, the number of computational studies for low-Miller-index, i.e., (111), (100) and (110) interfaces/grain boundaries is rather scarce.
Thomson et al. [5] investigated the interactions of gallium atoms in Σ=11 (113) grain boundary.
Also, for each entry the number of atoms and space group is given.

Bulk metallic materials possessing uniform grain structure with average crystallite sizes below 100 nm and grains limited by high-angle boundaries can be formed by a number of methods [2].
The first set consists of the samples after plastic deformation and the annealing at 575°С, 100 h (the numbers from 1 to 6).
Grain boundaries in ultrafine grained materials processed by severe plastic deformation and related phenomena, Mater.
Plasticity and grain boundary diffusion at small grain sizes, Adv.
Semionkin, Mössbauer Spectroscopy of Grain Boundaries in Ultrafine-Grained Materials Produced by Severe Plastic Deformation, Bull.

Due to relatively high sensitivity of superplastic properties to a grain size, the superplastic forming is normally applicable to ultrafine-grained (UFG) materials only.
The HAB fraction was measured to be 84% of total grain boundary area.
The microstructure also consisted of nearly equiaxed grains with high proportion of HABs but the mean grain size was measured to be ~2 mm.
Effect of superplastic deformation and static annealing on mean grain size Characteristics Superplastic conditions 300 °C 3.3×10-3 s-1 350 °C 8.3×10-3 s-1 400 °C 3.3×10-3 s-1 Mean grain size in grip section on base material side, μm 2.1 2 10 Mean grain size in grip section on stir zone side, μm 2 >100 >100 Mean grain size in near-necking region, μm 2 2.1 20 At 350oC, the mean grain size of the base material was measured to be ~2 mm (Table 1, Fig. 6a), i.e. the grain growth behavior was nearly unchanged.
Acknowledgements This work is supported by the Ministry of Education and Science of the Russian Federation under the agreement №14.584.21.0023 (ID number RFMEFI58417X0023).

The five phases are the extradendritic melt, the solid dendrite and interdendritic melt inside the equiaxed grains, the solid dendrite and interdendritic melt inside the columnar grains.
The averageand, grain number density of equiaxed crystals (), and mold and ingot temperatures of the as-filled state are used to initialize the solution of the 5-phase simulation of ingot solidification.
As shown in Fig.3, the higher the number of jets, the more quiescent is the flow.
Increasing number of jets reduces the kinetic energy per jet.
The number density of equiaxed grains (Fig.7c) is high at the ingot core.