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Grain size, morphology and spatial distribution.
It is clear from Figs 4(a) and (b) that the number of Cube grains in the CR_A and IA_1 materials is not very high.
As is well established, depending on the size of the particles with which the recrystallizing grains interact, the number of potential nuclei may be increased by PSN or recrystallization may be inhibited by Zener drag [9].
That is, while the overall number of successful nuclei was significantly lower in the IA_1 treated material than in the case of the IA_2 treatment (compare Figs 4(b) and (c)), there was apparently a sufficient number of PSN-grains with sizes that exceed dcrit so that a more extensive development of the Cube texture was prevented (during the IA_1 treatment).
In fact, the number of Cube grains in the IA_2 material is higher than in the IA_1 case but the corresponding area fraction (16.8%) in the latter is not that different from that of the former (15.9%).

During the subsequent ECAP process, β- Mg17Al12 phase and Mg2Si was broken gradually with the increasing of ECAP pass numbers.
For the 4-pass processed sample, more grains were significantly refined, but distributed inhomogeneously, coarse grains are surrounded by fine ones, which is called as bimodal microstructure [15].
For 2-pass ECAPed sample, small part of grain was refined while β-phase is discontinuously distributed interaction of grain size and second phase make it have the similar corrosion behavior with the as-cast alloy.
With increasing of ECAP pass numbers, the corrosion type changed from pitting corrosion to general corrosion.
Saito, Improving both strength and ductility of Mg alloy through a large number of ECAP passes, Mater Sci.

So no matter how strong the electron beam was, it only irradiated 1-2 crystal grains.
Due to big residual stress around, the dislocation pinned and crossed crystal grains, and crack produced segregation for the exist of zirconia grains which consumed a part of fracture energy.
Grain-boundary sliding is another one of the deformations as shown in Fig.4(b).
In Fig.6 phase corresponds to a number of peaks.
According to qualitative investigation and indicators, the ground surface of Al2O3-ZrO2(n) is composed of α-Al2O3 with diffraction angles of 35° and 30°, t-ZrO2 and a small number of m-ZrO2 with diffraction angle of 28°.

With the cooling rate decreasing, when t8/5 = 60s, the original high angle austenite grain boundaries gradually disappeared, eutectoid ferrite grains occured at the original austenite grain boundaries, lath bainite, granular bainite and granular ferrite are generated in the original austenite grain.
As can be seen that when t8/5 = 30s, due to rapid cooling rate, the number of M-A constituent is little, and strip M-A constituent distributed in ferrite matrix directively (Figure.2a).
With the cooling rate decreasing, when t8/5 =60s (Figure.2b) , M-A constituent changes significantly, gradually change from strip to block, the number and density increased.
STE355 Steel Microstructure after Welding in the Grain Shell and its Effect on Toughness.
Zr microalloyed HSLA steel coarse grain heat affected zone microstructure and properties.

The fracture toughness of hot press sintered Al2O3 was, therefore, higher than that of pressureless sintered Al2O3, because the total amount of bridging stress and stress shielding effect increased with increasing magnitude of microcrack deflection and the number of interlocking grains.
Total number of nodes and elements were about 70,000 and 17,000, respectively.
Crack face bridging, i.e., grain bridging, was rarely observed.
The fracture toughness of hot press sintered Al2O3 was, therefore, higher than that of pressureless sintered Al2O3, because the total amount of bridging stress and stress shielding effect were increased with increasing magnitude of microcrack deflection and the number of interlocking grains.
(4) The total amount of bridging stress and stress shielding effect were found to increase with increasing magnitude of microcrack deflection and the number of interlocking grains.

The samples subjected to different holding times were differentiated by the numbers of hours following the denotation, e.g., S1-1 and S2-1 for the samples holding for one hour.
Care must be taken in selecting the H-P parameters, σ0 and ky, because they will be influenced by quite a number of factors concerning the materials characteristics, and the values in the literatures differ significantly.
Concerning the continuity conditions imposing multiple glide on polycrystal, M was taken as the Taylor orientation factor, being related to the number of operative slip systems in the polycrystalline aggregate [24, 25].
If we define a volume in the structure with hard particles on grain boundaries of ductile polycrystalline matrix to deform as an integral, apparently, the number of operative slip system in the hard particles is zero, and then the total number of slip systems in the whole volume is reduced.
We define this volume element as the one consisting of the composite of ferrite matrix and cementite particles distributed homogeneously on the grain boundaries, and the number of both grains and particles are sufficient in the element.

The more cycle times, the grain is smaller.
Experimental results Fig. 1 shows the relationship of alloy plasticity and cycle number. (1) Elongation: without making any treatment, the extension rate is 35%.
With the increasing of cycle number, the elongation increased.
The more cycles, the grain is finer [14].
In addition, it is significantly, the number of second phase particles that gotten after the five cycles is more than that after three cycles.

It is revealed that a bimodal grain structure, i.e. ultrafine grains accompanied by micron-sized grains was developed after 4 passes.
After three passes, as shown in Fig. 1(c), there was a significant increase in the fraction of HAGBs and a large number of equiaxed grains formed along the grain boundaries between elongated large grains, so it can be concluded that most of these smaller grains were formed by the fragmentation of the elongated grains and some of them were further refined from the fine grains formed in the first and second pass.
After four passes, as shown in Fig. 1(d), a large number of ultrafine equiaxed grains formed along the HAGBs of the remaining coarse grains.
The above results further demonstrates that a bimodal grain structure comprising of ultrafine grains (with grain sizes less than ~1 μm) and micron-sized grains was achieved in the present study.
Acknowledgements The authors would like to acknowledge the financial support from Research Council of Norway, under the FRINATEK project ‘BENTMAT’ (Project number 10407002) and China Scholarship Council (201406080011).

Causality analysis of the differences in local toughness was done with samples marked with circles and sample number, as shown in Fig. 1.
Ferrite grains in this locality were coarse with mean grain size d= 0.250 mm.
The microstructure in the vicinity of the fracture and slab surface was coarse grained with mean grain size d= 0.177 mm.
For the brittle sample D22 the mean grain size was d = 0.0221 mm, while the ductile sample D21 had grain size d = 0.0156 mm.
Metallographic evaluation of seeming grain size

During single electron beam irradiation to 3.6dpa the dislocation loops with lower number density were formed near the grain boundary.
At 3.6dpa the loops with higher number density were formed.
The smaller size void appeared with higher number density at 8dpa.
Fig.3 shows the dose dependence of void size and void number density.
Fig.2 Void structure observed in Fe-Cr-Mn(W、V) alloy irradiation at 673K to 10dpa Fig.3 Dose dependence of average size and the number density of void in Fe-Cr-Mn(W、V) alloy Irradiation-induced solute distribution near grain boundary.