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Reheating of the billet before forming process must be accurate and quick to avoid uncontrolled grain growth.
Profitable conditions of plastic deformation in partly liquid state appears when liquid fraction forms very thin layer at the grain boundaries, which is like ‘lubricant’ and makes the plastic deformation to be the result of rotation and slip of relative grains.
A globular grain structure can be obtained by: SIMA (Strain Induced Melt Activated), SC (Spray Casting) or MHD (Magneto-Hydro-Dynamic Process) method [5].
Ram speed is numbered v1=2mm/s, v2=1mm/s respectively.
This reduction is as big as metal grains are fine and more globular what depends from quality of MHD stirring method application.

Coatings with a number of characteristics, e.g. wear and corrosion resistance are of great practical importance.
Irradiation was carried out in the following conditions: energy density of electron beam in the pulse – 30 J/cm2; pulse duration – 200 µs; number of pulses – 20 at the first stage; energy density of electron beam in the pulse – 30 J/cm2; pulse duration – 50 µs; number of pulses – 1 at the second stage.
In the volume and on the boundaries of martensite crystals, as well as sub-grains of α-phase there are particles of the second phase.
The surface of the deposited layer modified by intense pulsed electron beam is destructed when wear resistance testing due to a great number of micro-pores.
Electron-beam processing of the welded surface when melting the surface layer results in formation of a poly-crystalline structure, the grain sizes of which vary 0.2 µm to 2 µm (Fig. 2, b).

From * Corresponding author Table 2, we can see that Vickers hardness numbers decreased as the aging time increased.
As aging time increased, grain size as well as precipitation hardening at the grain boundary increased.
The white line in Fig. 3 Shows dimension of grain size.
Strength and hardness of materials are closely related with the size of the grain boundary.
The size of the grain increased according to degradation of the material and deposition of S and Cr at the grain boundary.

At the sintering stage, powder properties have great effects on the phase formation of spinel, neck growth, grain growth and the formation of grain boundary.
For samples sintered at the same condition A, there exist many abnormal large grains and grain growth in sintered cores for samples sintered from coarse powder (Fig.3 1A).
With improving the powders more uniform and finer, the homogeneity of grains and uniformity of grains size have been greatly improved (Fig.3 2A, 5A and 6A).
The number of large grain decreases and then grows up, shown in Fig.3 1A, 1C, 1E.
Meanwhile, the grain size and uniformity of sample 6 reach optimum and there is no obvious change among Fig.3 6A, 6C and 6E.

The results were compared before and after the heat treatment process for addition of nano particles and without nano particles. 1 Introduction Despite a number of competing materials developed during the last 25 years, aluminium retained its top position in several areas of application, especially in the aerospace sector.
Most research on Al-Si alloys aims to improve their physical, mechanical and corrosion properties by adopting various techniques, such as, modification, grain refinement and heat treatment.
Fig.1 An electrically operated squeeze casting machine 4 OPTICAL MICROSCOPY AND GRAIN SIZE ANALYSIS All castings were sectioned at a height of 25 mm from the bottom and the freshly cut surfaces of the castings were used for optical microscopy and grain size analysis.
Optical micrographs were taken using a metallurgical microscope (Olympus Colour view BX51-N33MU, Japan with image analysis software, analySIS-FIVE) and grain size analysis was carried by the linear intercept method.
Gruzleski, Grain refinement mechanisms of hypoeutectic Al-Si alloys, ActaMaterialia, 44 (9) (1996) 3749-3760

The main model parameters are interfacial energy for nucleation, total nucleation sites and nucleation locations (homogeneous nucleation in the matrix, at dislocations, and at grain boundaries).
Outputs of this model are volume fraction, number density, mean size, and size distribution of precipitates.
Figure 2 shows the predicted evolution of Mn-concentration in solid solution, the mean radius and the number density of the precipitates.
In terms of the number density of the precipitates in the batch annealed condition, the model prediction is quite close to the measurement by Flemming, 1.4E19 versus 1.0E19/m 3.
The number density by Anselmino, 1.7E18/m 3, is far lower than the model prediction.

Results The grain size has a significant effect on the strength of the alloy.
It can be concluded that the recrystallized grain size changed a little with the increase of PS.
Moreover, the strength of aluminum alloy was not sensitive to the change of grain size [15,16].
Therefore, the interference caused by the average recrystallized grain size was eliminated.
Precipitation behavior and high strain rate superplasticity in a novel fine-grained aluminum based alloy, Mater.

Strength gradually decreases with the number of passes (UTS decreases from 275 to 250 MPa after 4 passes while YS decreases from 239 to 207 MPa.
Superplasticity of fine grains: Methods to promote grain refinement are an important research field.
With 50% deformation, the grain size was fine and uniform at 20~30µm.
But when the deformation was 40 and 60%, the grain size was 10~100µm with grains being quite coarse in some areas.
A large number of fundamental and common technological problems currently block the processing and technological development of wrought magnesium alloys.

Another observation is that the crack formation region does not show clear changes of grain size.
The relationship between the vacancy concentration and temperature 0 50 100 150 200 250 300 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Temperature (0C) Vacancy concentration when the number of thermal vacancies present in the system reaches a certain level.
The segregation enrichment of Mg might be a key factor leading to cracking because Mg segregation at grain boundaries increases the embrittlement of the grain boundaries due to the decrease of cohesive energy of grain boundaries [5].
When a crack is formed at a Mg enrichment grain boundary, its propagation would attract much more Mg atoms due to the much lower energy at a surface than at a grain boundary.
Zhang, First-principles Investigation of Mg Segregation at ∑ =11(113) Grain Boundaries in Al, J.

Recently, the DSR has been conducted on the Mg alloys for enhancing the ductility by texture control and/or grain refinement [4,6,7].
The grain sizes were determined by analyzing the optical micrographs with a line-intercept method.
It is clear that the cracking occurs along the shear band in case of the small RPP (8%) and it develops with increasing the rolling pass number.
The shear bands consist of fine grains and the remaining regions exhibit coarser grains resulting in an inhomogeneous microstructure.
This result indicates that the formability of the Mg alloys at room temperature is dominated by the texture rather than the grain size.