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Keywords: Microalloyed Steel, Austenite Grain Growth, Coarsening of Carbonitrides Abstract: Austenite grain growth in microalloyed steels is governed by the coarsening of fine precipitates present at grain boundaries below the grain coarsening temperature.
The grain boundary area is the main source of energy for grain growth process; therefore, the system will evolve to reduce its grain boundary area [1].
Larger grains will grow at the expense of the smaller ones.
Although these models are based on a number of physical and geometric assumptions that differ among the models, all of them can be generalized using the following general equation, n crit f r D φ= . (1) where critD is the average critical 3-D prior austenite grain size (3DPAGS), r and f are the mean radius and volume fraction of carbonitrides, respectively, and φ depends on factors such as the geometry of precipitates and austenite grains or coherency between precipitate and matrix.
On the other hand, if precipitates are distributed in austenite at random, due to the low volume fraction of the sample occupied by the grain boundaries, the number of precipitates present in the matrix will be higher than those located at grain boundaries.

When the carbon content increases from 0.27% to 0.35%, the number of the spherical VN or V(C,N) increases obviously and the size of it varies from 20~100nm to 45~105nm, while the number of flake VC and fibrous VC decreases significantly and the length of fibrous VC shortens from several micrometers to nanometer size.
The effective precipitation of V(C, N) in austenite may induce intragranular ferrite and fine ferrite grain [1,2].
With the increase of carbon content, the number of spherical precipitates obviously increases, and the size of it becomes larger.
The main useness of them is precipitation strength, which is the most important way of strength only second to fine-grain.
Furthermore, the smaller size and the more number of precipitate can get bigger strength effect.

Temperature and humidity are main factor in grain analysis of ecological storages.
Through observation on temperature and humidity of each part of grain heaps, variation laws of internal environments and features of grain heap environments are reflected.
This network relies on the complexity of the system, by adjusting the connection between the numbers of nodes within the relationship so as to achieve the purpose of information processing.
Artificial neural network is an adaptive information processing system composed of a large number of simple processing units connected in parallel non-linear.
A grain depot environmental data is in table 1 below.

Grain boundary internal friction peak in nan˚Crystalline aluminum studied by continuously changing-temperature J.N.
The IF peak is a grain boundary IF peak, which is ass˚Ciated with the diffusive grain boundary of Al/Al.
Nan˚Crystalline materials have many prominent properties owing to their large volume fraction of grain boundaries.
It can be concluded that the IF peak is caused by the grain boundary sliding which is accommodated by the Al/Al grain boundary sliding.
There are a large number of grains with different orientation in nan˚Crystalline aluminum, during the internal friction measurement of periodic stress, grain boundary viscosity sliding constraints and limits, only in the appropriate temperature, i.e., , the internal friction peak appears.

During the present study, needle like grains of hematite have been observed within the top layers of a number of external oxide scales formed during simulated reheat of 316L stainless steel.
A number of recently published papers have shown that EBSD is an effective method for characterising scales formed on mild steels [7, 8] and more recently on stainless steels [9].
This would suggest that formation of the needles and the hematite grains at the grain boundaries are related.
It shows that the three needle containing spinel grains are of differing orientations to one another and that the needle like grains also differ not only to their parent grain but also to the needles formed in other spinel grains.
At 1300°C the needle like grains all have a similar misorientation angle to their parent grains of approximately 56°.

Positron lifetime calculations using the PAW method are highly sensitive to the number of valence electrons in the PAW dataset.
Depending on the cluster size, the number of atoms removed from the cell ranged from n = 1 to n = 40.
Coincidence-site lattice grain boundary Among the enormous number and complexity of grain boundaries, there is a special type known as coincidence-site lattice (CSL) grain boundaries, where several atomic sites from one grain align precisely with those in the neighboring grain.
Compared to random grain boundaries, CSL grain boundaries are thought to have lower energy due to their better atomic alignment, making them an important subject of study in grain boundary science and engineering [29].
In reality, there are an infinite number of possible lattice variants for grain boundaries.

A typical print out of the surface roughness of Al – 4 %Cu specimen Results and Discussion Effect of the Number of Rolling Passes on the Grain Size of Al and Al- 4 % Cu.
Effect of rolling passes on the grain size of Al Pass Grain size µm 0 120 1 63.2 2 104.5 3 120.2 (a) (b) (c) (d) Fig. 2.
Effect of the number of passes on the grain size of commercially pure A at 200X.
Effect of rolling passes on the grain size of Al Pass Grain size µm 0 94.9 µm 1 114.5 2 104.5 3 79.9 (a) (b) (c) (d) Fig. 3.
Photomicrographs of Al - 4 % Cu showing variation of its general microstructure and grain size with the number of passes at 200X Effect of the Rolling Process on Vicker’s Microhardness.

The intergranular fracture mode of TE indicates a weakening of the grain boundaries.
Existing studies have suggested that the segregation of residual elements, such as phosphorus, stannum, antimony, and arsenic, at the prior austenite grain boundaries is responsible for the embrittlement, a finding verified by a number of Auger electron spectroscopy (AES) studies [4,5].
Small carbide particles situated at the prior austenite grain boundaries and martensitic lath boundaries can be observed.
The number of these particles per unit area is greatest at this tempering temperature.
These small particles situated at the grain boundaries can be identified as cementite.

There is no significant improvement in alloy after the addition of grain refiners and / or modifiers.
There was no significant improvement in alloy after the addition of other grain refiners and / or modifiers.
There were no significant improvements in alloy after the addition of other grain refiners and /or modifiers.
Fig.4: Surface roughness Ra in µm v/s sample number of Al-Si alloys Drill tool dynamometer readings: The drilling operation was carried out by giving the spindle rpm as 500rpm and depth of cut as 5mm.
[4] Grain refinement response of LM25 alloy towards Al–Ti–C and Al–Ti–B grain refiners by G.S.

The effect of grain size in nanocrystalline alloys is difficult to analyze because challenges of controlling a number of other microstructure factors.
For this purpose, the effects of various microstructure factors on deformation behavior of nanocrystalline alloy need to be better understood, including grain size, grain interior composition, grain boundary composition, and grain boundary width.
As the grain size decreases to tens of nanometers, the deformation becomes dominated by grain boundary instead of grain interior.
At this stage, partial dislocations nucleate on grain boundary, rapidly pass through grain and get absorbed by opposite grain boundary.
Taylor, A unified approach to motion of grain boundaries, relative tangential translation along grain boundaries, and grain rotation, Acta Mater. 52 (2004) 4887-4898