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.% Ca addition, the phase of Al2Y is refined obviously and the phase of Mg17Al12 has a dramatic decrease in number.
It can be observed that the Mg17Al12 phase is distributed in the grain interior and on the grain boundaries and that the second phase Al2Y is diffused in the intragranular [7].
After T6 treatment, blocky Mg17Al12 is discontinuously distributed at the grain boundaries and punctate Al2Y phase is unevenly distributed, mainly in grain.
Those are illustrated on the two respects: the grain growth is suppressed and the generation number of β(Mg17Al12) can be reduced, and the second phase particles are dispersed in the alloy.
It is well known that large numbers of β(Mg17Al12) phases can barely promote the high temperature mechanical properties of Mg-5.5Al-1.2Y alloy.

%Mn strip had a quite large equiaxed grain zone, while other Fe-Mn strips mainly consisted of columnar grains grew from the surfaces.
No central equiaxed grains were formed, as shown in Fig.6(a).
A large number of substructures like the stacking fault and dislocation were observed.
There were only columnar grain zones within the Fe-11wt.
%Mn strip became smaller and columnar grain was more

The model of abrasive grain’s wear.
Abrasive grains move at a constant speed.
Fig.3 The relationship between grinding force and surface roughness The reduction of surface roughness is directly related to the number of active grains Ng and the shape of the grains.
Under these conditions, abrasive grains are worn quickly or can be extracted from the bonding phase which may decrease the number of real active grains Ng.
New grains are involved in grinding.

A number of specimens were obtained from different parts of the castings to evaluate microstructure, and both high dense and fine grain microstructures were found in the specimens.
The grain size is among 0.02 to 0.08mm.
It means that the structure is denser with quite finer grain microstructure than the Al-Cu-Mn alloy obtained from sand casting[5].
Hence, fine grains dense microstructures were achieved[6-8].
Microstructure analysis has shown that fine grains and dense microstructures were achieved in the fabricated castings

With the increase of annealing time, the number and dimension of metastable phase decreased at the same time.
With the increasing annealing time, both the number and dimension of metastable phase in as-solidified microstructure were decreased, Fig.4.
The energy at grain boundary is higher for where crystal lattice is seriously distorted, so the diffusion activation energy is lower at grain boundary.
Therefore, the atomic diffusion at grain boundary is easier and faster than that inside grain, so, metastable phase at grain boundary has transformed to stable phase firstly.
With the increase of annealing time, both the number and dimension of metastable phase decreased in as-solidified microstructure.

Pearlite nucleates in the austenitic grain boundary, bainite nucleates preferentially in the grain boundary and sometimes in the grain interior and martensite nucleates preferentially in the interface and generally in the grain interior.
Furthermore, the grain boundaries are the favorable channel of the diffusion, so the grain boundaries become the preferential nucleation sites.
It is obvious that the lath martensite can nucleate and grow not only in the crystal grain interiors but also along the crystal grain boundaries and crystal edges.
A large number of observations indicated that martensite can nucleate in the austenite crystal grain boundaries, the austenite crystal grain interiors, the twin crystal interfaces or the phase interfaces.
The experiments show that pearlite nucleates in the austenitic grain boundary, bainite nucleates preferentially in the grain boundary and sometimes in the grain interior, and martensite nucleates preferentially in the interface and generally in the grain interior.

We studied suspensions by means of zeta potential and grain-size measurements.
Grain size and zeta potential measurements were conducted by using a Malvern Zetamaster Nano-ZS.
Since each grain-size distribution contained 70 points, the number of datapoints for the grain size was 700 and the total number of datapoints in each dataset was 710.
For each approach, several datasets were built and analysed, depending on the number of considered suspensions.
Fig. 1: Ten subsequent grain size measurements on the same suspension, i.e.

The volume fraction of high-angle grain boundaries was about 57%.
However, the number of superplastic aluminum alloys is currently limited because of difficulties in producing an ultra-fine grain structure by conventional routes of thermomechanical processing [1].
The ultrafine grained structure stabilized by these nanoscale dispersoids is stable against grain growth under superplastic conditions [9,10].
In addition, grains tend to elongate along tension direction.
The uniform fine grain structure is necessary for frequent operation of GBS by shifting of the grain groups along the common grain boundary surfaces [1, 16].

Fig. 2a shows the S-N curves of applied stress amplitude versus number of cycles.
These fine grains are much smaller than the original grains (Fig. 1a).
Near this fine grain area, high density of low angle grain boundaries (white lines in Fig. 4b) have formed.
The size of “fine grains” depends on the stress concentration in the area and number of cycles.
Plastic deformation in the “fine grain, (b).

n is a dimensionless number and defined as the number of grains which could be always founded in a volume wherever as large as n times the specific volume per grain, which means that the grains are uniformly distributed at the scale of n times the specific volume per grain, within that volume, however, n number of grains are randomly distributed.
However, the actual number of abrasive grains remaining on the working surface is much less because the over-exposed grains would pull out during conditioning operation.
One is the areal density of grains number Nm ( T > t ) with the protrusion height T larger than the specified t , as shown in Fig. 6, which represents the cutting edge distribution Nm ( T > t ) in depth-wise, and also is one of the most important factors influencing on grinding process.
Bt=i=0Nmπ(rgi2-(t-Zi)2)　　 (1) In this Eq. (1), Nm represents the number of the protruding grains at the specified height t , and rgi and Zi stand for the grain radius and the center position of abrasive grains in z-axis, respectively.
From the information of these results, the areal density of grains number Na ( T > t ) of protruding abrasive grains with the protrusion height T larger than the specified t can be counted.