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Introduction It is well known that hexagonal close-packed (HCP) magnesium and its alloys have complicated deformation mechanisms, because deformation twins are activated to supplement the limited number of available slip systems for a homogenous deformation [1,2].
The microstructure and grain size of the solutionized alloy were examined by optical microscopy (OM) and the average grain size was found to be about 90 µm.
The {10.1} and {10.2} grain families, favorably oriented for basal slip, show the soft grain orientation behavior involving stress relaxation, while the {10.0} orientation reveals the hard grain orientation behavior taking on additional load.
The highest strain occurs in the {11.0} grain orientation.
In Fig. 3a, the lattice strains for all five grain orientations are linear up to an applied stress of ~30 MPa, after which the slopes of {10.2} and {00.2} grain families decrease as the grains start to yield.

Grain growth occurred during the solid solution process.
This kind of precipitation consumes solute atoms in the alloy, making the subsequent aging process only a little number of solute atoms being able to precipitate the Age-hardening phase.
In the crystal within the matrix grains and at grain boundaries also exist a large number of spherical particles seeing as C area, the spherical particles were segregation due to the temperature reducing and deformation stress and other factors in the forging process, by XRD analysis verified that the precipitated phase are another kind of intermetallic compounds, Mg5(Gd, Y,).
While the matrix grain size hasn’t grown up too much, there is well coordinating effect between matrix grains.
Grain Refining Mechanismin Mg-9Gd-4Y Alloys by Zirconium [J].

With the same total reduction, strength rised as total pass number increased in multi-pass rolling.
The grain size of the as-extruded material is displayed in Fig.1 (a).
At temperature 400�, although heavy reduction can promote grain refinement, deformation energy produced by rolling accelerates grain growth, which leads to a balance between refinement and growth of recrystallized grains [3] Total pass number.
It shows that the grain size is nearly same in spite of different total pass number.
It is thought that more pass number will lead to worse mechanical properties because of grain growth during repeated heating between passes.

It is widely accepted that the number of applied passes had a strong impact on the global deformation behaviour and on the intensity of grain refinement.
(Coalescence is the process by which two or more neighboring, slightly misoriented cells(grains) merge to form a single, larger grain).
At later annealing stages, due to the intense grain growth, some of the grains attains sizes grater that average grain size.
However, it needs to be noted that in some cases considerable grain growth is observed before the lamellar grains spheroidize [11].
The above process divides flat grains, makes their shape nearly globular, and it is responsible for orientations of new grains.

Due to the difference in the number of nucleation sites, martensitic transformation is greatly promoted in cold-drawn specimen rather than cold-rolled one. 1.
The mean austenite grain size was approximately 60 μm.
As a result, the austenite grains observed in the DD section keep an equiaxial shape.
This suggests that deformation twinning in multiple directions provides a number of nucleation sites for deformation-induced martensite over a whole grain, and this leads the promotion of martensitic transformation in cold-drawing rather than in cold-rolling.
Since a large number of nucleation sites are prepared for deformation-induced martensite by intersecting twin boundaries, martensitic transformation is promoted in cold-drawing rather than cold-rolling

During the meshing process the space was discretised and described with a 3D digital image composed of voxels (pixels in 3D) that can be labelled with the number of grains they belong to.
The grain sizes of workpiece were assumed to be 6, 45, 120, and 248 μm with two kinds of grain size distribution.
According to the grain hardness, grained heterogeneity can be figured out.
Generally, the grain-boundary volume within a metal polycrystalline increases when the grain size decreases.
These active dislocations intertwine in the grain boundaries during plastic deformation, so there will be a large number of mutually repelling dislocations intertwined if the grain size is small.

The common index was relationship between recovery rate and cold-heating circulation number.
The relationship between recovery rate and cold-heating circulation number of CuAlNi and CuAlNiBe was shown in figure 1.
Fatigue Life Cycle The number of cold-heating circulation of different alloys samples before fatigue fracture was shown in table 3.
Tab3 The number of cold –heating circulation of different alloys sample Alloy CuAlNiBe CuAlNi CuAlBe Single Crystal Polycrystalline Single Crystal Columnar Crystal Polycrystalline Number 487 7 465 237 45 The results in table 3 showed the fatigue life cycles of every kind of single crystal material were more than polycrystalline and columnar crystals obviously.
And the number of cold-heating circulation of CuAlNiBe single crystal was more than other alloys.

When the recrystallization is complete (), further grain growth takes place to reduce the grain boundary area per unit volume.
(2) where is DRX fraction, is strain for 50% recrystallization, is initial grain size, is recrystallization grain size, is growth grain size, and is average grain size.
The total number of element and node are 28116 and 6408, respectively.
Distribution of average grain size.
The grain size in the region Ⅳ is the finest compared with that of other regions and the average grain size is about 30 (μm).

Bold numbers reveal the exceeding of the minimum requirement from the standard ASTM B348-02 grade 23 for this property.
Boron effects a drastic reduction in grain size as visible in table 1.
These particles act as obstacles for grain growth by pinning of the grain boundaries [8-9].
The fatigue experiments reveal the effects of porosity and grain size.
The numbers in parentheses denote the amount of samples that survived at a specific stress level (run out).

Low angle grain boundaries with a minimum of 2° misorientation are shown on the maps.
In Fig. 1 a well-developed low angle grain boundary (LAGB) structure can be seen clearly across the whole of the grain.
Near the grain boundaries the contrast changes indicate the 50 µm 50 µm 100 µm 20 µm Journal Title and Volume Number (to be inserted by the publisher) formation of subgrains, but in the grain centres, there is little change in orientation contrast.
From Mean (°)Journal Title and Volume Number (to be inserted by the publisher) Results of in-situ hot deformation experiments In-situ tensile deformation SE images show the movement of grain boundary and the alignment of the boundaries during the early stages of deformation of the 4.98 % Mg alloy.
Stress driven grain boundary migration occurs at low strains, resulting in boundary alignment parallel to planes of high shear stress, and the development of a diamond grain morphology.