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Main factors controlling deterioration are initial chromium carbide size and their distribution along austenite grain boundary and chromium concentration distribution inside of grain.
For the corrosion resistance ability, fdc is smaller than 2.2 and chromium concentration at grain boundary is higher than 21 wt pct, because with the smaller fdc, grain boundary Cr concentration is too low, and the larger fdc, grain boundary is easily sliding.
The precipitated carbide along grain boundary is modeled by KJMA equation.
To calculate fdc, dcar is expressed as follows; dcar=3aInt (3) where a is austenite grain size with 30μm, Int is carbide total number.
The nucleation rate is related with the number of carbide.

The microstructure comparison of ultrasound and general cast-rolling shows that: The grain size of general cast-rolled lead strip is big; the grain boundary is coarse and the organization structure is uneven.
However, the grain structure is refined, smaller grains and uniform organization structure is acquired with ultrasound treatment.
Therefore another technology is needed which can improve the crystalline environment and refine the grains.
A large number of domestic and international researches showed that the effect of cavity and acoustic streaming can break the big dendrite structures, refine the gains and enhance the mechanical properties of metals [10-13].
The acoustic streaming intensifies the movement of melt flow leading to the grains conflict with each other.

However, rapid solidification/powder metallurgy (RS/PM) processing of magnesium alloys poses critical challenges due to the very high chemical reactivity of magnesium metal itself and a number of its important alloying elements.
The grain size ranged from 10-30µm, and the average grain size was about 20µm.
The dynamic recrystallization grain sizes depend on the initial grain sizes, and tend to decrease as the initial grain size decreases.
It's benefit for the dynamic recrystallization grain nuclear in primary grain boundary[7].
The fine dimple numbers are quite large.

If a small recrystallized grain structure is obtained at 600°C, the liquid filler metals diffuse and penetrate into many grain boundaries.
It seems that the initial large grains remained and the recrystallization occurred in the initial large grains.
The increase in equivalent strain leads to increase in dislocation density, the number of nucleation sites, and the forces driving recrystallization.
It seems that the deceased number of precipitates less than 0.8 µm in diameter leads to an increased number of nuclei near nucleation sites (deformation bands, transition bands, particles, etc.) for recrystallization.
It reveals the grain structure using 5° and 15° misorientation angles of the grain boundary.

These monolithic technologies are used to reduce part count as well as the number of fasteners, assembly time, and weight all of which lead to cost savings for the product.
Even though either of these processes would allow the number of components to be reduced by combining details, it was decided to keep the same number of major parts.
A fine grain version of 6Al-4V, with a grain size of about 1 µm, has been jointly developed by Verknaya Salda Metallurgical Production Association, VSMPO, in Russia and Boeing.
This fine grain material will also diffusion bond to standard grain alpha-beta alloys, as shown in Fig. 5, at 775°C using the same time and pressure conditions.
Fig. 6 Representative SPF heat shield details produced using fine grain 6Al-4V.

Then the alloys were subjected to ECAP in a tool with a channel intersection angle of 45° at a temperature of 450 °C along the BC route [20], the number of cycles was 6.
ECAP provides the formation of a homogeneous sub-fine-grained structure in the alloys, while the average grain size, decreasing 100-200 times, is 0.3-0.5 microns.
According to TEM data, grain boundaries free of dislocations are observed in the coarse-grained state.
After ECAP, a complex diffraction contrast is observed at the grain boundaries, which indirectly indicates an increase in the density of dislocations at the grain boundaries.
During mechanical tests, it was found that in the coarse-grained state, the tensile strength of the Ti49.5Ni50.5 alloy is 720 MPa, and after the ECAP increases with the number of passes and reaches a maximum (1350 MPa) for 6 passes, which is almost 90% higher than in the coarse-grained quenched state (Fig. 2).

Austenite final grain size was measured .
grain size.
The experiment also shows that steel with higher Nb content has lower grain growth kinetics and has the finer austenite grain size.
Higher cooling rate after hot rolling and recrystallization will produce finer autenite grain size, and steel with higher Nb content has lower grain growth kinetics and has the finer austenite grain size. 2.
Tech, vol 24, Number 2, (2008.)

The domain size is 3mm wide by 4mm high, giving a total number of 600×800 cells.
A thin layer of fine grains grew from prefixed seeds and only a few long columnar grains succeed in growing due to the competitive nature of the growth.
Equiaxed grains are formed immediately from a thin layer of fine columnar grains near the surface.
Density of nuclei in bulk liquid changes from 6.5×1010 (number of nuclei/m3) (Fig. 3 (a)) to 6.5×1014(number of nuclei/m3) (Fig. 3 (e)).
-4 -3.5 -3 -2.5 -2 2 2.5 3 3.5 4 4.5 -4 -3.5 -3 -2.5 -2 2 2.5 3 3.5 4 4.5 -4 -3.5 -3 -2.5 -2 2 2.5 3 3.5 4 4.5 -4 -3.5 -3 -2.5 -2 2 2.5 3 3.5 4 4.5 Log (G) [K/m] Log (V) [m/s] Log (V) [m/s] Log (V) [m/s] Log (V) [m/s] Log (G) [K/m] Log (G) [K/m] Log (G) [K/m] 1wt%Cu1wt%Cu 3wt%Cu 7wt%Cu 5wt%Cu 1wt%Cu Equiaxed Grains Equiaxed Grains Equiaxed Grains Equiaxed Grains Columnar Grains Columnar Grains Columnar Grains Columnar Grains Figure 4 Progress maps showing the effect of alloy solidification range on the CET: (a) open and filled diamonds indicate equiaxed and columnar grains for Al-1wt%Cu; (b)open and filled circles indicate equiaxed and columnar grains for Al-3wt%Cu; (c) open and filled triangles indicate equiaxed and columnar grains for Al-5wt%Cu; (d) open and filled squares indicate equiaxed and columnar grains for Al-7wt%Cu.

Grain boundary phases in Mg-Zn-Y-Nd-Zr alloys subjected to various heat treatments were characterized.
The mean grain size D determined by the linear intercept method is given in Table 1.
The a-Mg grains which appear dark in the image due to lower Z are surrounded by Zn and Y enriched eutectic which appear bright due to higher average Z number.
The Zn and Y enriched regions at grain boundaries consisting of W and I phase are denoted by the term grain boundary phase (GBP) in the following text.
DSC peaks for various processes are labeled by numbers.

In the ARB processed sheet, the grains are elongated along roll direction (RD) and the thickness of the elongated grains gradually decreased with increasing the number of ARB cycles.
Sample Annealed 2 Cycles 4 Cycles 7 Cycles 10 Cycles 13 Cycles dt[µm] 35 5.1 2.1 1.2 0.61 0.49 dl[µm] 33 16.3 7.1 3.5 1.7 1.4 In the sheet ARB processed by 2 cycles, a number of dislocations generated in the original grains and it made subgrain structures.
The fraction of the UFG regions increased with increasing the number of ARB cycles, i.e. strain.
(3) The reduction of the grains thickness and length was carried out with increasing the number of ARB cycles.
(4) In the ARB processed sheet,the rate of grains thickness decreasing was more than the rate of grains length decreasing and the grains were elongated along RD.