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The high speed camera is employed to capture the motion of the balls and measure the impact velocities by counting the number of frames.
A layer-up structure can be generated at the near surface area, not only formatting the grade structure with refined grains [3], but also large compressive residual stress along the thickness direction [4].
As observed from the recorded frames, the ratio of balls running along horizontal direction trends to be increased as the number of balls raised in Section B.
Since the number of balls within unit space is increased, scale of Section B has been extended that even height at top surface is covered.
Lu, Microstructure and Evolution of Mechanically-Induced Ultrafine Grain in Surface Layer of Al-Alloy Subjected to USSP, Acta Mater., (2002),50, 2075–2084

Optimal neural network architecture is based on the number of hidden layers and the number of nodes in each layer using a trial and error method.
The best solution was found at training cycle number 15.
The resulting microstructure is a mixture of very fine grains of ferrite.
The average grain size ranges between 10-15 µm.
At each trial, it varies the number of neurons in the hidden layer and retain the best models.

The grain size of semi-sintered ceramic is generally not greater than 300nm, close contact with a strong interaction and neck formed between grains is visible clearly.
The porous network structure formed between the grains with irregularly pores but communicate with each other.
The smaller abrasive grain size on grinding needle , the larger the number of grains that participated in grinding, which will reduce the residual height and surface roughness of processed surface, but the grinding efficiency will be reduced.
Physical grinding needle and the photo of diamond abrasive grains that were magnified 50 times are shown in Fig. 5.
Through a large number of experiments, reasonable grinding and grinding parameters were established.

Nonetheless, it is necessary to have a further study on the effect of parameters such as background pressure, sputtering pressure, sputtering power on the film surface morphologies, microstructures and grain size in the DC magnetron sputtering process.
There are less grain interior defects, columnar tissues are separated from one another, and a large number of interfaces and gaps are distributed.
This diffraction character indicates that the ZrCoCe films are composed of amorphous or nanocrystalline grains, while numerous grain boundaries and irregular-packed atom regions facilitate oxygen diffusion into the bulk during the activation, resulting in lower activation temperature than the bulk getter.
When the background pressure at the 10-2-10-3 Pa orders of magnitude, the residual gas molecules tend to gather in dislocations or grain boundaries, thus the growth of most grains is limited.
A small number of grains are not pinned and the grain grows abnormally, leading the average grain size reacted on the XRD spectrum is larger.

In high strength AlMgSi alloys additions of Mn and Cr lead to the formation of dispersoid phases whose primary functions are to improve fracture toughness and control grain structure.
The size and number density of the dispersoids was determined using high contrast back scattered electron images from a JEOL 7001F FEGSEM and Adobe Photoshop Extended CS4 Win EULA.
Increasing the homogenisation temperature and time led to a reduction in the number density of the dispersoids and an increase in the size (Figure 2).
Increasing the temperature to 570°C and the time to 12 hours, lead to an decrease in the number of small dispersoids (< 100nm) with most dispersoids being in the range of 200 to 400nm.
The dense dislocation network in the proximity of the dispersoids indicates the pinning effect of the dispersoids which leads to reduced recrystallization and grain growth.

The 83-GHz system is used for rapid sintering of ceramic powder compacts to produce polycrystalline materials with limited grain growth.
SEM micrograph of Y2O3 sample We have demonstrated that the continuous microwave polyol system can be used to produce sizeable quantities of fine-grained yttrium oxide.
A small amount of silica is added as a sintering aid that promotes uniform grain growth and densification through the formation of a liquid secondary phase at grain boundaries.
SEMs of these samples indicate grain sizes of 5-7 µm for the one-hour processed samples and approximately 10 µm for the two-hour processed sample.
The grain boundaries appear to be clean, although there are a number of trapped pores.

In the Cu matrix equiaxed grains of about 300 nm in diameter are observed (Fig. 1a).
The similar effect of annealing was observed in a number of publications, this process starting at temperatures as low as 3500C [6-8].
However Nb grain size distribution in the former seems more uniform and the sizes are smaller in agreement with previous observations [9].
Along with the evolution of fine structure, regularities of texture development were studied by X-ray analysis on a number of composites (samples 9, 11, 13, 15).
However in a number of publications only one axis, <111>Cu, is reported [12,13].

Imposing certain pressure to the right wall (orange grain)of tool model(green grain),there should be always maintain a certain contact pressure between chip and tool, Given chip(yellow grain) constant upward flow velocity, which entered from the lower pole of the periodic boundary layer, then flow along the tool surface, arrived at the upper end of the periodic boundary layer then broke away from abrasion zone, and then entered from the lower end of the periodic boundary layer, reciprocating, the continuous flow was formed.
Crack Crack Crack (c) (b) (a) (a) vc=57m/min； (b) vc =84m/min； (c) vc =103m/min Fig.3 DEM simulation of tool wear at different cutting speed (ap=0.3mm，f =0.2mm/r) Crack Crack Crack (c) (b) (a) (a) ap =0.1mm； (b) ap =0.2mm； (c) ap =0.3mm Fig.4 DEM simulation of tool wear at different depth of cut (vc=84m/min，f=0.2mm/r) Detached particle Crack Fig.5 Partial enlargement of cracks in Fig.3(a) Under the condition of that cutting depth was ap=0.3mm, the number of peeled particle from tool, and the number of micro-crack and wear rate varied along with the cutting speed, were shown in Fig.6.In the picture we get that with the increase of cutting speed, cutting tool micro-crack number and particle peeling number and wear rate were increased first and then decreased.
The tendency that the number of shedding particles and micro crack of tool and wear rate vary with the cutting depth is shown in Fig.7, which the cutting velocity were vc=84m/min and vc=103m/m respectively.
It can be seen that the number of shedding particles and micro cracks and wear rate increase with the cutting depth’s augment.
(a) micro-crack numbers (b) detached particle numbers (c) wear rate Fig.6 Effect of cutting speed on micro-crack numbers, detached particle numbers and wear rate (a) micro-crack numbers (b) detached particle numbers (c) wear rate Fig.7 Effect of cut depth on micro-crack numbers, detached particle numbers and wear rate Summary The tool-chip wear discrete element model was established, and the cutting process was dynamic simulated under different condition.

When strain ageing occurs, a great number of “fresh” dislocations appear in steel; if they are fluent enough, they are capable to react with the atoms of carbon and nitrogen.
As can be seen from Fig. 3a, separate black dots (iron carbides) exist in the volume of grains.
There exist practically not any iron carbide grains at the grain edges.
As can be seen from Fig. 3b, the amount of cementite particles increased in the volume of grains.
Exudations at the grain edges increased as well.

INTRODUCTION The composites of aluminium alloys reinforced by SiC (particles, whiskers, short fibers) are promising candidates for a number of aerospace and automotive applications due to their high stiffness and strength, and good wear resistance.
Namely, the matrix grain size is reduced by particles acting as nucleation sites during solidification.
In addition, the grain size is reduced by the formation of subgrains when dislocations are rearranged into boundaries within the grain.
Subgrains are formed in those grains with high dislocation density surrounding a SiC particle.
The fractographs (Fig. 5) show many small voids associated with oxide particles present along the grain boundaries.