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Its drawbacks include the need to do a large number of passes and a low welding speed.
Microstructure of metal of the coarse grain region, immediately adjoining to the fusing zone, is a mixture of upper and lower bainites with grain of score 4-6 (see Figure 5, a).
No ferrite interlayers along the grain boundaries were revealed.
Size of the coarse grain zone varies from 0.7 to 1.3 mm.
Structure of metal of the fine-grain zone is mixture of smaller (score 7-10) grains of bainite and ferrite.

The basis of manufacturing stone casting silicate materials is controlled crystallization of silicate melt that is organized in such a way that nucleation occurs within the melt and the final product has a fine grain structure.
The basis of manufacturing stone casting silicate materials is controlled crystallization of silicate melt that is organized in such a way that nucleation occurs within the melt and the final product has a fine grain structure.
It is established that this catalyst (oxide Cr2O3) causes liquation of silicate melt into two phases, and this phenomenon causes the appearance of crystallization centers and facilitates growth of crystal grains.
The function of heat treatment lies in provision a maximum number of formed crystallization centers that causes fine–grained structure; the necessary degree of crystallization and specified phase composition that is in other words allocation of crystalline phases with specific properties.
Manufactured under controlled crystallization and with the addition of the catalyst stone casting silicate materials have a fine grain structure, improved mechanical strength and are more resistant to acids and alkalis as well [8] (Table 2).

Chen et al. [6, 7] argued that the loading aging process can result in fine, dispersed precipitated phase in the Al-Sn-Mg-Cu alloy but can also widen the precipitate-free zone (PFZ) at the grain boundary, increasing the size of the precipitated phase at the grain boundary and elongating the crystal grains to promote stress relaxation.
At the same time, due to the incompatible deformation between different grains and between grains and carbides, dislocation pile-ups formed around grain boundaries and carbides, as shown in Fig. 1 (e) and Fig. 1 (g).
Unlike the unstrained samples, the high-density dislocations gathered at the grain boundaries began to move from the boundaries into the grains after tempering at 100 °C for the 10% prestrained sample (Fig.3 (b)).
In the meantime, driven by the concentration gradient of the complexes between the grain boundaries and grains, the vacancies and solute atoms at the grain boundaries also begin to move into the grains (Fig. 3 (e)).
Furthermore, a large amount of carbide precipitation occurred in the crystal grains (Fig. 3 (h)).

The grain sizes of the primary Si were observed and measured by KH-2200 high magnification video microscope.
Table 2.Experiment results of Zl109 alloy modified by Al9Fe3P master alloy Number of experiment 1 2 3 W1 (Weight of ZL109 alloy)（kg） 180 180 180 W2(Weight of Al9Fe3P master alloy)（kg） 0.54 0.72 0.90 W1/W2×100% 0.3 0.4 0.5 Modification temperature(°C) 760 760 760 Modification time 30 30 30 Sample inspection before casting good good good Degree of operating convenient easy easy easy Distribution of primary Si well well well The maximum grain size of primary Si（μm） 76-85 58-66 56-63 The average grain size of primary Si（μm） 48 40 38 Metallurgical grade of sample 4 3 3 The primary Si in ZL109 alloy are coarse with polygonal lumps or plate shapes and the eutectic Si are thick slice shown as Fig.1 (a).
Table 2 shows that the microstructures of pistons maintained at level 4 by adding 0.3wt. % Al9Fe3P master alloy, whose maximum grain sizes of primary Si were among 78-85μm and average grain sizes of primary Si maintained 48μm(Fig.1(b)).
The microstructures of pistons maintained at level 3 by adding 0.4wt. % Al9Fe3P master alloy, whose maximum and average grain sizes of primary Si were among 58-66μm and 40μm.
Thus a large number of fine and rounded primary Si would form in molten alloy during its solidification process, which could improve mechanical properties and hardness of the ZL109 piston alloy.

Each increment in plastic flow is accompanied by an increment in the number of dislocations beneath the indenter.
Consider a row of grains.
By comparison with the soft grains, the hard grains require less extension to achieve the same stress.
To re-attach the row of grains to their neighbours, and thus restore cohesion, material must now flow from the soft grains to the hard grains.
Of course, these stresses can be relieved by grain-boundary diffusion over distances equal to the grain-size itself.

It is believed that cube regions in the deformed material are fragments of the original cube oriented grains in the starting material or they can originate by a rotation mechanism where other grains can rotate to the cube orientation during deformation.
In order to clarify the above issues, it is important to understand the deformation and recrystallization behaviors of cube grains in a polycrystalline aggregate which has hardly been investigated as compared to number of studies on cube oriented single crystalline materials.
Both the orientation maps show the presence of RD-rotated cube ({013}<100>, denoted by CRD and highlighted in purple) grains.
The absence of cube texture in the SSCT is attributed to the inhibited nucleation of cube grains as may be clearly seen from Fig. 3.
Minamino, ARB (Accumulative Roll-Bonding) and other new techniques to produce bulk ultrafine grained materials.

An important physical parameters at milling are the average grain size and indicative grain size parameters.
Average grain size is the parameter of the largest grain size which remain on the sieve downfall to 50% of a total amount of grains.
The definition for the indicative grain size parameter is the same, but the largest grain size which remain on the sieve downfall is compared to 63,8% of a total amount of grains.
Milling the samples were carried out for the specified milling times and amounts at the number of 45 rotations / min.
Measurement parameters - average grain sizes R50% and indicative grain sizes R63,8% from first phase are shown in the Table 5.

Hydrothermally produced BT nanopowders show a number of structural characteristics not seen in powders prepared by conventional solid-state reaction at high temperature.
Morphology and grain size were investigated by SEM and TEM.
HRTEM images (a) a typical lattice image of nanocrystalline BT grain of size of 75 nm in sample A, (b) a surface profile HRTEM image of part of a BT grain with size of 80 nm in sample B.
This may be caused by the high strains in the grains.
A uniform diffraction contrast across single grains was observed.

is grain boundary energy and is surface energy.
Considering grain growth at final stage sintering, Ng, the number of grains for 1g of porous component, is substituted in Eq. 4 as follows: (5) Vp is the pore volume per grain, SG is the surface area of a grain,is the grain boundary area reduction due to the pores per grain and Ap is the surface area of pores per grain.
A weighing factor of 0.5 is prescribed for the surface area of a grain as every grain boundary is assumed to be shared between two adjacent grains.
Assumeing Kelvin’s tetrakaidecahedron grain, Ng is given by where is theoretical density of the material. 2.3 Grain growth Densification usually takes place with simultaneous grain growth, particularly during the final sintering stage.
While some of the pores are located on the grain junctions, a number of the pores migrate to the two-grain interface and some separated intragranular pores are formed after they break away from the grain boundaries.

The grain refinement of the primary crystal α makes it changes from coarse columnar dendritic structure to fine equiaxed structure, the mechanical properties of the alloy greatly improved.
When insulating 12h, the grains further coarsening, and some of grain began to deteriorate roundness, and differences between the sizes of the grains become larger, that is, grain uniformity decreases.
When the alloy was heated to 540 ℃, the primary α becomes irregular, large differences in the size and dimensions, the grain coarsened.
And the insoluble phase in the alloy grain boundaries and intragranular dissolve more fully, components are more uniform, the mechanical properties the better.
Conclusions There are the main columnar α phase, eutectic (α dendrites + eutectic silicon) in B refined alloy Al-7 wt% Si, heat treatment makes the dendrite α smaller, the number increases, eutectic particles tends to round, the structure and hardness have been changed.