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At above 880℃, the grains grow owing to the heating.
The number of grain boundaries decreases, and the boundaries becoming flat and form angles close to 120ºwith the increasing holding temperature.
Under the temperature of 1100℃, the average grain size is less than 250μm; from 1100℃ to 1250℃, the grain size grows gradually; and there is an abrupt growth at 1250℃, as the grain size increases rapidly.
Consequently, the grain size increases tremendously.
At 1220℃, obvious grain growth tendency can be observed.

At room temperature, high angle boundaries (HAB) are observed within some of the initial grains, and not necessarily close to the grain boundaries.
The development of intersecting microshear bands that subdivide the original grains into numerous domains is believed to be the primary grain fragmentation mechanism in MAC.
Barrelling, which tended to worsen with each additional compression, limited the total number of passes and hence the cumulative applied strain.
On the whole, the series of curves suggests that the flow stress reaches saturation after a certain number of passes.
This could indicate the start of the formation of new grains.

The Microstructure and Texture of Fine Grain High-Strength IF Steel after Continuous Annealing ZHANG Li-wen1, a ,WANG Zhen-min2,b ,ZHANG Hong-mei ,HOU Jue3,c School of Materials and Engineering ,University of Science and Technology Liao Ning,An shan 114000,China azhanglw1983@163.com Keywords: fine grain high-strength IF steel; texture; holding time; EBSD Abstract: In this paper,the fine grain high-strength IF steel after cold-rolling and continuous annealing was studied.The microstructure under different holding time of fine-grain high strength IF steel was observed by the OM and the TEM technology.
Compared with traditional IF steel, the fine grain high-strength IF steel increase the carbon content and add the appropriate element Nb to fix the solution element(C,N).On one hand, these large number of precipitation of Nb precipitates can effectively prevent the movement of grain boundaries and sub-boundaries, inhibit grain growth and refine the grain.
The grains of 120s and 180s samples have begun to grow, and recrystallized grains have grown up along the rolling direction.
The grains of tested steel are largest and evenly in 120s.
Therefore, the optimal holding time is 120s for the fine grain high-strength IF steel after continuous annealing.

Study on the weldability of ultra fine-grained steel has become the focus of research[3].
Fig. 1 shows the macrostructure of resistance spot welding joint for ultra fine-grained steel.
When columnar grains grow to a certain extent, because of the front liquid metal is far from electrode surface, the heat dissipation difficulty and slowly cooling hinder the rapid growth of columnar grains.
At the same time, the exist of forge-delay force impels the melted metal to shock, resulting in the solidified grains fragmentation at the advanced edge of liquid-solid interface, not only hinder the grains growth, but the grains fragments can act as nuclei for new grains to form, thus, the grain structure in fusion zone will be refined.
The nugget zone almost consists of coarse martensite, and the existing of forge-delay force during the cooling process causes the plastic deformation of nugget, promoting the number of dislocations.

In order to clarify the difference between the grain boundaries in ARB-Cu and equilibrium boundaries, calculated atomic structure of symmetric tilt grain boundaries with <110> common axis (<110> symmetric tilt grain boundary; <110> STGB) in Cu were used.
Therefore, it is expected that the mechanical properties of the ARB processed material having numerous number of grain boundaries are governed by the atomic structure of the boundaries.
However, the atomic structure of the grain boundaries in the ultrafine grained materials fabricated by the SPD has been rarely studied.
Furthermore, in order to compare the grain boundaries in the ARB-Cu with equilibrium grain boundaries, the MD simulated grain boundary structures of copper [4] were used.
The misorientation angle between adjacent grains was about 14˚.

Although a considerable number of studies have been made on the mechanism of the preferred growth of Cube texture [6-8], there is lack of spatially resolved crystallographic data directly related textural development at an early stage of recrystallization.
In the Sample-A, the fraction of Cube orientation increased sharply from 558K to 578K with increase of the number of new Cube grains.
To put it another way, one explanation for the preferred-growth orientation, such as Cube in the Sample-A or S in the Sample-B, can be that the number of growth grains is more than that of shrinkable grains.
On the contrary, regarding the shrinkable orientation, such as S in the Sample-A or Cube in the Sample-B, the number of shrinkable grains is more than that of growth grains.
Even on a large grain that grew remarkably, some grain boundaries were hardly moving in the direction of the surrounding grain that had higher grain boundary mobility.

It is proposed that the high strength and plasticity of the ultra fine grained nickel is related to a deformation mechanism involving grain boundary sliding and grain rotation.
Average grain size (D) and number (N) of diffraction pattern spots of Ni as a function of treatment.
Since the number of spots is proportional to the number of grain in the investigated area, it is seen that at 200° � a uniform grain growth begins in the material.
The coarse-grained material shows brittle failure with traces of dislocation sliding on grain surface.
On the other hand, in the UFG structure dislocation sliding across the grains is suppressed due to the small grain size.

The MF technique has been used successfully for the grain refinement in a number of alloys including 7475 aluminum alloy and pure polycrystalline copper etc. [7].
The grains orientation transition still could be found in some grains.
The lack of a homogeneous and clearly defined array of equiaxed grains in many materials after SPD processing makes it difficult to full characterize the ultra-fine grained microstructures in terms of grain size.
While once the cell or the subgrain boundaries have been identified, the grains can simply be defined as the number of points which make up the grain, and the area of a grain in square shape can be calculated by multiplying the number of points making up the grain by EBSD test [10].
The mean grain sizes as a function of strain determined by the EBSD grain reconstruction method is shown in Fig.4.

From this figure, it is known that output waveforms of grain 1 and grain 2 are closely same output voltage.
Comparing depth of cut 20mm as shown in figure 6 and 40mm as shown in figure 7, it is known that measured results of 40mm are larger output voltage and more the number of output waveforms than results of 20mm.
It is considered that the number of contact abrasive grain with wire is increased with the increase of the depth of cut.
In figure 8, compared the calculated results of AE occurred positon and measured results of actual grain cutting edge position, it is known that the number of cutting edge is increased with the increase of the depth of cut.
Acknowledgment This research was supported by a research grant (Year: 2013, Subject number: R1310) from the Mitutoyo Association for Science and Technology.

The straining and moderate ECAP temperature caused the cementite lamellae fragmentation and spheroidzation as number of passes increased.
In the past decade, a number of the various sever plastic deformation (SPD) techniques have been used to refine structure of metals and alloys.
The AISI 1045 steel billets were subjected to warm ECA pressing at T= 400°C and to higher number of passes, N = 4, 5, 6 respectively.
The more grown and already equiaxed grains of high angle boundaries, with less dislocations in grains are documented in Fig. 5.
The dislocation substructure in ferrite grains was modified upon dynamic polygonization, however the low angle boundaries are still in ferrite grains.