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Optical microscopy was used to characterize the morphology of the aluminum grains, the dispersion of SWCNT and present pores in the samples.
The results indicated that the density and hardness of the samples are increased with the increase in the number of extrusion passes and the use of back pressure.
The factors investigated were: the presence of CNT; the number of extrusion passes; the extrusion route used between passes; and the use of back pressure.
The ECAE passes in route A of the sample promoted the alignment of aluminum grains and CNT clusters in the direction of extrusion.
The refinement of CNT clusters occurred similarly to the grain refinement.

The results showed that composite coatings had a compacter and refiner surface than ordinary Pb-Sn alloy coatings; the addition of CNTs increased the number of crystal cores and changed the directions of crystal orientation, which resulted in a fine network structure.
The surface of the composite coatings had refine grains because of CNTs inclusion.
Crystal orientation even more cluttered for the increased number of CNTs, it is difficult for Pb-Sn alloy grains to grow up to the larger size, therefore, and it led to grain refinement.
(1) Homogeneously dispersed CNTs in the bath was the basis for access to high quality composite coatings, they increased the number of nucleation in the electro-deposition process, therefore, the composite coatings had more dense surfaces than ordinary Pb-Sn alloy coatings
(2) CNTs changed the direction of grain growth; it is difficult for grains to grow up to larger size, which led to grain refinement of composite coatings.

The fig.4 also demonstrates the grain size.
Variation of grain size of Mg2Si with annealing temperature Fig.6.
Milling can induced a large number of intragranular defects.
Also Milling makes grain in high energy state, which causes grain stability decreased.
Large number of defects provided more nucleation positions for Mg2Si.

It shows that the grain size decreases with increasing Nd content.
And when Nd content increases to 1.5 wt.%, the number and size of precipitates increase and segregate as block morphology, as shown in Fig. 2 (d).
As shown in Fig. 1(a), the grains in Zn-25Al-5Mg-2.5Si alloy are coarse and adding 0.4wt%- 1.2wt% Nd, the grains become smaller(Fig. 1c-e).
According to this relationship, the smaller the grain size, the higher the strength.
When Nd content is 0.8wt.%, the grains refining effect on the alloys is optimum.

They present a granular surface, as observed by SEM, with a broad range of grain sizes.
The bigger grains observed in the micrograph of figure 1b) have an average size of 647nm.
The grain sizes are in the range 20nm to 100nm.
Since the average grain sizes of the phases composing the films are below 100nm and the SEM micrographs show the existence of a significant number of grains up to ~650 nm, this again indicates the presence of a broad distribution of grain sizes in the films.
Thus, the magnetic moment of these isolated grains is more difficult to align along the applied magnetic field, particularly for the smaller grains (<40nm) which are monodomain.

People always hope to get the most ideal results with least test number in the development of new material.
In the preparation stage, the grain abnormal growth and the sintered loose microstructure will reduce the mechanical properties of materials.
If the sintering temperature is too low, the sintered body can't fully densified and otherwise the grain growth is serious.
When the duration time is too short, the material will not be fully densified and otherwise the grains will grow seriously.
The mechanical property table is consisted of the basic information such as serial number and volume fraction of the matrix, additive, auxiliary phase and binder phase, the serial number of sintering and preparation and the mechanical properties of the ceramic cutting tools.

The parameters used in the HCPEB surface treatment were as follows: the accelerating voltage 27 kV, the numbers of pulses 35, the pulse duration 5 μs, peak current density 6J/ cm2.
Clusters grow outward until contacting adjacent grains.
However, these nodule units are not grain while boundaries of the cluster organization are not grain boundary.
A large number of craters are found when samples are observed at a certain tilt angle.
As for grain size, the surface grain size can be less than 200nm after electron beam irradiation.

With the increasing of quenching temperature,the grain grows,the impact property is decreased.
Compared to the original sample and the subcritical quenching sample, in addition to differences in organizational, the grain size of its size, the degree of dispersion of various other phases have undergone great changes.
And the tempered martensite can be clearly seen from a former into a plurality of grains.
At a temperature of 950 ℃, Compared with non- temperature quenching samples, although its organization exists in the grain size decreasing trend but there is a substantial degree of uniformity improvement,as shown in Fig 3(c),4(c) and 5(c).
(c) (b) (a) Fig.5 Original sample and subcritical quenching sample crystalline phase organization chart × 1000 (a Original sample b 910℃ quenched sample c 950℃ quenched sample) 3.2 Mechanical properties and hardness results Table2 The effect of quenching temperature on the mechanical properties of EH36 number Normalizing process Yield strength Rel/MPa Tensile strength Rm/MPa Elongati-on A/% -40℃ impact energy AKV/J hardness（HRC) Grain size scale A TMCP 385.2 541.1 22.7 56.5 36.8 9 B 910℃quenched samples 372.1 510.4 35.5 72 63.1 10.5 C 950℃quenched samples 380.6 515.3 35.2 70 53.5 10 The tensile tests,impact tests and hardness tests on original samples and subcritical quenching asmples were done,the average test data was shown in table2.

Effect of a Si Additive on an Al Grain Boundary: a First-principles Investigation Ying Zhang1, Guang-Hong Lu1,a, Han Zhang 2 Tianmin Wang1, Shenghua Deng1 and Xuelan Hu1 1 School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083, China 2Department of Physics, Peking University, Beijing 100871, China a lgh@buaa.edu.cn Keywords: Al grain boundary; Si; electronic structure; first-principles Abstract.
The electronic structure of an Al grain boundary (GB) with Si as an additive has been investigated by a first-principles method.
Impurity can largely change the mechanical properties of the Al alloys by its segregation in grain boundary (GB).
Italic numbers indicate the Al-Si atomic distances.
S A B Q x y (a) Fig. 1 Supercell of an Al 9(221)/[110] Σ tilt grain boundary.

In as cast samples, main alloying elements Si and Cu were located between aluminum grains along grain boundaries.
At higher heat treatment temperatures, precipitates were observed to have grown in size due to Ostwald ripening and their number per unit area was reduced (Figure 5).
Precipitate size is larger at this temperature but their number is reduced.
The grains became larger and spherical.
Precipitate size is larger at this temperature but their number is reduced.