Search results

When the grain size is approaching the material thickness, individual grain significantly affects the deformation behavior of the material [1].
This suggests that the effects of the individual grain properties become more significant as a number of grains through the thickness decreases.
This is because the surface grains become dominant with decreasing t/D.
Since the surface grains are less restricted, dislocation motion is hardly blocked by grain boundary.
This leads to the decrease of the void formation and that of the number of dimples on the fracture surface[3, 13].

The number of non-zero submatrix is written as Nk, in which k is taken 1, 2, 4, 8, … , 2 j , namely taking the size of 1, 2, …., 2 j pixel as side length to divide the submatrix, thus obtaining the box numbers N1, N2, N4, … , Nk.
The microstructure in the central of the ingot basically consists of particle-like or globular-like grain, as shown in Fig.1a.
The microstructure along the radial direction of the ingot has some changes: from particle-like or globular-like grain in the central area changing to rosette-like grain in the transition area.
The microstructure in the transition area mainly consists a b c of rosette-like grain and mixes a small quantity of globular-like grain, as shown in Fig.1b.
It is seen from Fig.1c that the microstructure in the edge area consists of the rosette-like grain and a few of dendritic-like crystals which do not fully change into rosette-like grain.

Quantitative grain size evaluation of such heavily twinned structures is difficult.
However it is fairly clearly seen that there a large number of grain 25µm-50µm in diameter.
There are numbers of grains in excess of 100µm.
Any number of additional passes does not provide a stronger driver for recrystallization.
There certainly isn't shortage of high angle grain boundaries or potential nucleation sites.

The exclusion of crystal water left a large number of pores, which make the whole samples structures loose and porous.
We also found that the grain size are uniform respectively at this temperature.
Much more liquid-phase appeared at 1500°C, which can make grains contact closely.
The grains grow up obviously and the sintering effect shows outstanding.
A large amounts of liquid phase appeared, and the number of pores significantly reduced, most of which are closed pores.

Experimental results show that Sn-Cu solder organization contains a large number of Cu6Sn5 graphic, while Sn-Ag-Cu graphic is IMC Ag3Sn graphic.
It can be seen from the figures, microstructure distribute a large number of floc structure.
It can be seen from the Fig. 4(a), the dislocations are observed at the grain boundary.
For the Sn-Ag0.3-Cu0.7 specimens, some IMC particles are observed in the grains, as shown in Fig. 4(b).
At the same time, it can be seen from the Fig. 4(c), a large number of IMC particles are observed in the grains.

Large number of dislocations generated in the Al-Si grains due to heavy plastic deformation during the high energy ball milling.
Formation of several sub grain boundaries occurred in the individual Al-Si grains due to the rearrangement of dislocations.
Thus grain refinement took place due to the formation of sub grain, which eventually transformed into submicron and nano-sized grains [15].
It can be predicted that these sub-grain and low angle grain boundary formation occurred during high energy ball milling of the as- received Al-Si powders.
The restriction of grain boundary movement and grain growth imparted by primary Si could assist in improving the mechanical strength of the nanocomposite.

(4) where N and N0 are the total number of pores and the number of penetrating pores along the solidification direction of a rectangular sample with 32mm(length)×11.5mm(width)×5mm(height) dimention.
It is obvious that most of the gas pores distribute at the grain boundaries.
Generally, there exist some grain boundary grooves because that much oxides and impurities are inclined to accumulate at the grain boundaries.
When the solidification velocity is too fast to make the hydrogen have enough time to diffuse into the pores at the grain boundary, a new gas pore will probably nucleates inside of the grain.
The microstructure shows that most of the gas pores distribute at the grain boundaries because of the existence of grain boundary grooves, only a few pores are located inside of the grains.

As the feed rate increases, the number of grain grinding in a certain area per unit time decreases, the surface quality decreases, and the surface roughness increases [3].
The higher the spindle speed, the greater the linear velocity of the grains, which reduces the maximum grinding thickness of a single grain in the grinding process.
The increase of the feed rate reduced the number of grains passing through the specified width and more areas were incompletely machined, which increased the surface roughness.
Therefore, the number of repeated processing of the grain on the previously processed surface is increased, the height of the residual material on the processed surface is reduced, and the surface roughness is reduced.
The grains repeatedly move up and down on the processed surface.

Figs. 1(a-c) show places, where grains of the Ti-containing phase are absent, and Fig. 1b shows Ti-based grains and the material structure around them.
Note that MgBx inclusions are better seen in the composition (COMPO) or backscattering electron image (BEI) (when the phase having bigger Z number looks brighter), while MgBO inclusions are better seen in secondary electron image (SEI), possibly, due to the similarity of their and the materials matrices Z numbers.
Fig. 1(d) shows the diffusion area in a Ti grain located in the material synthesized at 1050 oC.
After the synthesis the grains of all powders with Ti-based additions (points 2 in Fig. 4 and 1, 2 in Fig. 5) contain a certain amount of Mg even in the middle of the grains, thus, confirming the diffusion of Mg into TiC and Ti-O and, that, the diffusion is faster into TiC and TiO grains than into Ti grains.
The intensity of Mg diffusion into Ti-O or TiC grains is higher than that into Ti grains.

The grains were mostly equiaxed dendrites with a grain size of about 50 μm.
In the weld zone, the number of Al3Er particles was relatively small.
The Al3Er formed at the grain boundary of the weld zone was much less than the Al3Er phase of the parent metal zone, and the effect of hindering grain growth to fine grain strengthening was not obvious [6].
There was a large number of coarse columnar crystals near the weld line along the weld line.
In this case, it is impossible to form a sufficient Al3Er phase with Al to suppress grain growth and thereby to achieve fine grain strengthening.