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The Effect of Magnetic Field on Kinetics of Grain Boundary Grooving in Iron E.
It was shown that external magnetic field of 5 kOe slows down the kinetics of grain boundary grooving in iron at 750 °C by about one order of magnitude.
The average grain size after this high-temperature annealing was 30 µm.
AFM topography image (a) and the line profile taken along the white path (b) for Fe sample annealed for 2 h at 750 °C in magnetic field of 5 kOe. 0 1 2 3 0 10 20 30 wc=1.75 µm (a) Number of GBs w, µm 0 1 2 3 0 20 40 60 Number of GBs w, µm (b) wc=1.01 µm the magnetic field leads to the diminishing of size of the GB grooves, which, according to Eq. (1), is associated with the decrease of surface diffusivity.
Watanabe in "Recrystallization and Grain Growth", G.

But after T6 or annealing treatment, its dimple number increases evidently.
And the grain size of AZ91 alloy is obviously refined because of the occurrence of the dynamic recrystallization during hot extrusion.
And the T6 treatment of as-extruded alloy makes the grain size homogeneous and grows lightly.
The fracture of extruded sample is obviously ductile because there are a lot of dimples at the fracture surface, and after T6 treatment or annealing treatment, its dimple number increases evidently.
But after T6 or annealing treatment, its dimple number increases evidently.

Fig. 3: Grain size distribution in all samples.
Significant grain growth occurred in all annealing cycles.
The fact that the grain sizes increased so drastically during magnetic annealing suggests that the field had a considerable effect on grain boundary migration and hence the grain growth kinetics.
The grain size increased with increasing field strength, suggesting that the magnetic field accelerates grain growth under these conditions.
Acknowledgments This work was supported by the MRSEC Program of the National Science Foundation under award number DMR-0079996.

When cooling rate is 2~5°C/s, the microstructure is mainly based on granular bainite and ferrite (Fig. 2b, Fig. 2c); as cooling rate rises further, the number of ferrite declines gradually yet bainite increases and lower bainite (LB) appears (Fig. 2d).
When the peak temperature of the second pass of double-pass coarse grain region is 1000°C (higher than Ac3), that is the supercritically reheated coarse grain HAZ (SCGHAZ).
The grains of ICCGHAZ remain coarse as that of primary coarse grain region, which is also one of the reasons leading to decreased toughness [8].
When the peak temperature of the second pass of double-pass coarse grain region is 650°C (lower than Ac1), that is the subcritically reheated coarse grain HAZ (SCCGHAZ).
(3) To avoid forming a large number of martensite due to rapid cooling, and to reduce welding joint cold cracking sensitivity, the weld preheating temperature should be controlled between 100°C and 150°C when X100 pipeline steel is field welding

To satisfy this condition, the operation of at least 5 independent slip systems in each grain is necessary or having a sufficiently large number of grain boundaries, allowing various shifts and rotations that take place, e.g., during the superplastic flow, is necessary [7].
Doing so we take into account that the size of sub-grains is much smaller than that of grains.
We replace the sum of cosines of angles by the product of the number of boundaries (the upper limits of the sums) and the cosine of the average angle.
Then the number of boundaries is defined as М g = L/ dg and M f = L/ df, where dg and df are the average size of grains and low-angle fragments, respectively.
Size of low-angle fragments and grains.

Fig.1a illustrates the grain size was about 50-200nm.
These structures were not composed of a single grain, but made of several grains.
It is clear that every cellular structure contains a number of fine particles(grains), four grains having strong diffraction contrast are marked as 1, 2, 3, 4 in the figure.
Fig.3a presents one grain morphology in dark field mode.
Who will be dominant is determined by a number of conditions.

It was found that a surface of titanium samples tested on the vibratory stand was covered by very large number of microcracks which in a later stage of the research leads to the erosion of the material.
The average grain size was approximately 20 µm (Fig. 3).
Results of the EBSD evaluation of the Ti99.7 titanium structure: a) the inverse pole figure map, b) the basic triangle, c) the inverse pole figure for ND, d) area fraction distribution of the grain size, e) number fraction distribution of the grain size The Ti99.7 titanium exhibited a good cavitational resistance upon testing on the vibration stand.
In the further step, an effect of uplifting and collapsing of titanium single grains took place leading to a detachment of whole grains or their agglomerates (Fig. 5c-d).
The cavitational destruction of Ti99.7 samples tested at two different stands begins at grain boundaries of the a phase and slowly grows toward an interior of grains leading to a surface damage.

Compared with the low-nitrogen steel, the number of precipitates in decreased significantly and the size increased obviously in the high-nitrogen steel.
Besides, a small amount of 90~260nm irregular particles distribute on the grain boundary.
Nearby the high energy grain boundary, the dislocation density is high.
The number of precipitates was obviously decreased, and the size of which was larger than that of low-nitrogen steels.
Ultra-fine Grained Steel-Theories and Technologies of Structure Fined[M].

Figure 1 (g), (h) of ZK60 and ZK60 +1.0 Y morphology of two alloy extrusion products, we found that both alloys extrusion occurred after dynamic recrystallization, which ZK60 alloy extruded After the abnormal grain growth, and grain ZK60 +1.0 Y Y rare earth alloy added after the relatively small, large grains mixed with very fine recrystallized small grains, which is mainly due to the black alloy ZK60 +1.0 Y reticular formation of crystalline zinc-rich phase was squeezed after crushing second phase particles and fine particles, pinning grains and dynamic recrystallization grain growth inhibition dual role, it can effectively refine rare-earth Y alloy ZK60 tablets.
Figure 1 (e), (f) ZK60 and ZK60 +1.0 Y for the two-state microstructure T5 alloy extrusion products, extruded products after aging treatment, ZK60 alloy grain boundaries within the grains and particles are precipitation, the grain boundary more clearly, after ZK60 +1.0 Y alloy after aging treatment, the organization tends to be uniform, fine recrystallized grains have grown little tendency to precipitate particles number obviously.
In the extrusion process, the alloy, rare earth alloy, magnesium can play an effective role in the modification, i.e., refinement of the grain structure, so that the average grain size is reduced, since the number of grain boundaries depends directly size, therefore, the impact of grain boundaries on plastic deformation resistance of polycrystalline starting directly reflected by the grain size.
Figure 1 (g), (h) shows that adding the refinement of rare earth alloy Obviously, an increase in the number of grain boundary dislocations motion by the resistance increases, thereby enhancing its mechanical properties, extrusions aging treatment dislocations generated during extrusion, sub-crystalline alloy beneficial compounds dispersed second phase precipitation, aging can be on the basis of maintaining the tensile strength, yield strength of the alloy greatly improved, so ZK60 +1.0 Y alloy extrusion products should adopt the artificial aging treatment.
Effect of grain refinement on tensile ductility in ZK60 magnesium alloy under dynamic loading [J].

Fig. 4 shows the relationship between average slip strains and the number of cycles.
In the results of PRI-BSL cyclic with EQ-hardening, activities of both slip systems decrease with increasing the number of cycles (Fig. 4 (a)).
(a) (b) (a) (b) (a) (b) Fig. 4 The relationship between average slip strain and the number of cycles at =0.7 % in the model PRI-BSL cyclic with CRSS ratio of 1:1.1.
If there is any spaces between crystal grains after the deformation, mechanical constraints exist to conform the grain boundary of one grain to that of the other grain.
(a) (b) (c) εyy σyy σyy (a) (b) Grain 1 Grain 2 Grain 1 Grain 2 Fig. 7 Schematic diagrams of deformed shapes of crystal grains when the grains are separated at the grain boundaries.