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Type-I AEs with higher frequency components were detected during the pit growth and supposed to be produced by falling-off of surface grains due to intergranular attack, while a number of Type-II AEs (approximately 12,500 counts) with low frequency components were detected during SCC propagation and supposed to be produced by cracking of the chromium oxy-hydroxides.
We concluded that AEs were produced by falling-off of grains.
No AE data in the three gray bands means the exceeded memory capacity of the personal computer, since a number of AE signal was produced during this period.
The first AE was detected at 320 ks and the number of AEs increased gradually.
Cracking of the oxide produces a number of secondary AE.

Grain boundary element formulation.
Given a volume bounded by an external surface and containing grains, two kinds of grains can be distinguished: the boundary grains, intersecting the external boundary, and the internal grains, completely surrounded by other grains.
Let and be two adjacent grains.
The present formulation requires only meshing of the grain surfaces.
The grain size is ASTM G=12 (calculated number of grains per : [12]).

In such a set-up, the heat is extracted by a number of laminar water jets placed at regular intervals along the length of the run-out table [1].
The average grain sizes were measured to be 3.2, 2.8 and 2.5 m for ACC, UFC+ACC and UFC, respectively.
The increase in the density of high angle grain boundaries can lead to more effective strengthening by grain refinement because the presence of low mis-orientations between some grains may contribute to the reduced ky value in comparison to the ferrite grains with high mis-orientations [5].
Therefore, the better grain refinement strengthening can be achieved by UFC than by ACC.
By using UFC, the number of NbC (with the size of 5 nm) has been increased as compared to the cases of ACC and UFC+ACC, resulting in obvious refinement of precipitates.

The reason of this the dislocation density is bigger near by the grain boundary than inside the grains.
The number of grains, the diameter of the grains, and the boundary interface were measured by the image analyzer software.
Where is eutectic along the grain boundary there are much more new grain.
In order to distinguish the non-deformed original grains from the DRX grains, the recrystallized grains are defined as grains having an average diameter of <50 μm and the volume fraction of fine grains Vf is defined as follows [6]: Vf=Total area of individual fine grains AfTotal sampling area Ai Fig. 11.
The nucleation and grain grow of recrystallized grains occur along the eutectic phase.

The diameter of a crystal grain of AZ31B-430 is larger than that of AZ31 B-O.
The diameter of a crystal grain of AZ31B-200 is larger than that of AZ31 B-O.
The diameter of a crystal grain of AZ31B-430 is much larger than that of AZ31 B-O, and the form of a crystal grain also changes.
The number of load cycles, which generates a crack from an initial-crack tip, is shown in Table 3.
We define the number of load cycles when half crack length exceeds 10μ m as the crack generating number of load cycles.

However, if the number of stacking layers and/or the reduction per pass increases some advantages will be expected [3].
Ia increases with the number of passes, which means that the severity of the process also does.
Evolution of the average intensity Ia with the number of passes in the ARBed samples.
Equiaxed cells/(sub)grains with diameter smaller than 1 µm are seen.
However, the cell/(sub)grain size of the three deformed samples is very similar.

The number of guide trough is 6 to 10.
Condition of soybean accumulation: After observing in the warehouse, the number of cumulate grain piles in the squat silo is six, the distribution of grain piles is shown in Fig. 5.
By observation, we can know that the first grain pile is maximum, the next is the fifth grain pile, and the sixth grain pile is smaller than the fifth grain pile, but it relatively larger than the second, third and forth grain pile.
The main reason of the middle heap largest: The number of original design for branches are ten but the test use five branches at present.
That is to say, the blanking in the middle from one point finally become multi-point, grain and impurity can distribute in a number of grain piles.

Furthermore, when the strain reaches a value of 4, a significant number of ultrafine grains have formed with the fraction of the HAGBs increasing continuously with strain.
A larger number of ultrafine grains were noticed in the region of higher strain, indicating that these grains are formed by a process of fragmentation/subdivision of initial grains.
It may be noted from Fig. 3(a) that even at a strain of 0.5, ultrafine grains, though few in number, have formed at the original grain boundaries and their volume fraction increases with increasing strain.
(I). purely elongated grains; (II). elongated grains with newly generated grains; and (III). newly generated grains.
Considering the large number of defects in ultrafine grained materials, it is appropriate to consider the grain boundary diffusion as the controlling mechanism of ferrite grain size, we obtain the relationship: ( ) 2/1 tDTH gb=α (3) The constant strain rate (ε& ) deformation at high temperatures can be divided into an amount of instantaneous plastic deformation (ε) and static annealing for a given period ( tt / ; εε=& ).

It can be seen the grain size of 1#, 2#, 3# are relatively small.
At the same time, Ti-Zr combined deoxidation process used in the production could form a large number of Ti-Zr composite fine particles which could pin austenite grain boundaries in the welding process to inhibit austenite growth, and to promote acicular ferrite nucleation during cooling [6].
Fig. 7 Three-dimensional reconstruction of acicular ferrite grains and a part of a big austenite grain, showing the partitioning of an austenite grain by acicular ferrite laths or plates [8] Effect of preheating on the toughness of CGHAZ.
The fine-grained mixed microstructure has very good impact toughness.
Wu, Effect of acicular ferrite formation on grain refinement in the coarse-grained region of heat-affected zone, Materials Characterization, no. 61, pp. 726-31, 2012

The grain sizes of Al and Mg alloys were reached to 875 nm and 656 nm after 3 cycles.
Grain size distributed and hardness analyzed.
The grain size was decreased as the number of cycles of the ARB process was increased.
Ultra-fine grained Al/Mg compound alloys whose mean grain size were about 875nm (Al) and 656nm (Mg) were successfully produced by the 3 cycle ARB process.
Grain size of the Al and Mg with different ARB cycles.