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In addition, with the increase of Sr addition, the ductility was improved and it was observed that the number of cleavage steps and secondary cracks decreased on the fracture surfaces of tensile samples.
Samples were homogenized at 550 oC for 30 minutes to delineate the grain boundaries.
(3) With the increase of Sr addition, the number of cleavage steps and secondary cracks is decreased in the as-cast samples, which improves the ductility of the alloys.
Mccartney , Grain refining of aluminum and its alloys using inoculants, Int.
Stjohn, The Role of Solute in Grain Refinement of Magnesium, Metall.

The precipitates on the grain boundaries are ellipsoidal-shaped and those in the austenite grains are needle-shaped.
Besides, precipitates start growing from grain boundaries to austenite grains and there has been a small amount of precipitates inside the austenite grains as shown in Fig. 2.
Then the precipitates connect along the grain boundaries until all the grain boundaries are filled with precipitates (Fig. 4b).
With the aging time continuing to increase, the number and size of precipitates in austenite grains increasing.
The precipitates on the grain boundaries are ellipsoidal-shaped and those in the austenite grains are needle-shaped.

The above results indicated that the trace amounts addition of La and Ce mixed rare earth can refine the α-Al grain size of the Al-0.75Mg-0.6Si aluminum alloy.
The main factors that determine the α-Al grains size are the number of the heterogeneous nucleation cores and the cooling rate of the Al-0.75Mg-0.6Si aluminum alloy.
The enrichment of La and Ce rare earth elements can make the solid - liquid interface leading edge to produce a component cooling zone and improve the nucleation rate of α-Al grains [8].
Finally, the enrichment of La and Ce rare earth elements in the α-Al grain boundary can also hinder the α-Al grain growth, which leads the α-Al grain refinement.
With the increase of La and Ce mixed rare earth additions, the tensile strength and elongation of Al-0.75Mg-0.6Si aluminum alloy increase gradually due to the grains refinement.

Careful inspection of the as-pressed samples by TEM showed that various grain sizes were achieved in the ECAP samples.
For example, the best microstructure for the 1421 alloy, as represented by the minimum grain size, was observed after pressing at 370°C where the grain size was ~0.3-0.4 µm.
The alloys pressed at other temperatures have exhibited visibly lower superplastic elongations [3,4]. 0 10 20 30 40 50 60 0,00 0,02 0,04 0,06 0,08 0,10 Number Fraction Misorientation Angle (degrees) 1420 Alloy cross section 0 10 20 30 40 50 60 0,00 0,02 0,04 0,06 0,08 0,10 Number Fraction Misorientation Angle (degrees) 1420 Alloy longitudinal section Fig. 2.
From Table 4 one can see that there is intensive grain growth in all these samples.
Summary From the results obtained one can conclude that, in addition to grain refinement, a very important pre-requisite of the enhanced superplasticity is a presence of precipitates and formation of high angle grain boundaries.

Figure 4 shows the changes of Fx, Fy and Fz with sliced line number.
Fx shows almost no change with line number.
type is non-active diamond grains with little protrusion, and the third is dropped diamond grains.
speed and number of sliced lines. 4.
At a high wire speed, the normal force, the number of active diamond grains and the workpiece surface roughness were reduced.

The coating surface has a large number of grains with various sizes.
The SEM micrograph of the surface of the sample (Fig.1)shows that the coating surface has a large number of grains with various size.
The size of the grains gradually increases with increasing duty cycle, and the surface becomes coarser.
It is worth to note that many bigger grains accompanied by bigger pores.
The surface coating has a large number of pore and compact layer shows itself a good combination with substrate magnesium alloy

The reason of this likely is the decreasing of the nucleation sites at the austenite grain boundaries and inside the small austenite grains.
The number of the intersections of the parallel test lines and the ferrite-ferrite or ferrite-pearlite boundaries per unit length was measured parallel and perpendicular to the orientation axes.
(1) where ( )pLP = number of the intersections of the investigated particles and the test lines parallel to the rolling direction, ( )nLP = number of the intersections of the investigated particles and the test lines perpendicular to the rolling direction.
It was found that by increasing the degree of deformation, the amount of the elongated ferrite grains increases and the grain size is decreasing.
The number of the parameters in the regression model was decreased based on the multicollinearity.

It is well established that compared to the coarse-grained materials, the fine-grained materials show a higher resistance against fatigue-crack initiation [11,12].
It is shown that the (β-ST+900°C WQ) sample shows a large number of martensite lathes distributed in β coarse grains.
During USSP process, as strain increases, dislocation density increases, and the initial grains were divided into large number of nanograins with high angle boundaries until the process of dislocation accumulation is balanced by dislocation multiplication [23].
Gu, Ultrafine-grain metals by severe plastic deformation, Mater.
Suresh, Grain size effects on the fatigue response of nanocrystalline metals, Scr.

The cube-texture fraction is plotted against the ratio of the average grain size to the initial grain size.
Microstructures for investigating the effect of fraction and average grain size The Monte Carlo Potts model can be also used to examine the influence on grain growth in quasibinary systems of both the relative average grain sizes and the initial texture fraction.
This artificially forces the growth of cube grains.
Cube grains are shown in light gray.
Acknowledgements This work was supported by the National Natural Science Foundation of China under contract numbers: 50671052 and 50371041.

The typical high-temperature ductile fracture morphology is related to both aggregation and growth of the large number of microscopic cavities and dimples.
Titanium alloy is typically designed for a moderate temperature (not exceeding 500℃), which prevents its wider use in air vehicles with high Mach numbers.
In addition, cavities are likely to form at grain boundaries, especially at triangle grain boundaries.
The Ti55 titanium alloy mentioned in this paper contains rare earth phase grains that provide both advantages and disadvantages: On one hand, they create an pinned effect to restrict growth of grains.
According to Fig. 6b, a large number of serpentine glide bands exist on walls of both large and small dimples.