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As shown in Fig. 1 (a), the grains of MA alloy were relatively uniform.
After cold working, the grains of the alloy with a strain of 25% became longer along the tensile axis, as shown in Fig. 1 (b).
With increasing temperature of heat treatment for the cold drawn alloy, the grains became larger and uniform again.
Fig. 1 (c) shows the grains of the cold drawn alloy after heat treatment at 950℃ for 10minutes.
As shown in Table 2, specimen No. 2 had the largest number of surface cracks and the largest CGR.

The results indicated that the fracture of the rod is induced by the unqualified chemical composition: a large number of inclusions which distribute in grain boundaries reduce the material plasticity and toughness, and eventually cause fracture.
The segregation of s along grain boundaries can weaken the gain boundary strength and induce the embrittlement eventually.
A large number of inclusions can be observed homogeneously distributed in matrix from Fig.4.
The results indicated that matrix metallographic structure is ferrite and pearlite, and the grade of grain size is 7-9, whether horizontal or vertical section.
(3)A large number of inclusions which distribute in grain boundaries reduce the material plasticity and toughness, and eventually cause fracture.

The grain boundary suffers severe corrosion, moreover, a number of grains peel off, i.e. the dark spots in Fig.2(a).
It is because the strength that makes grains interconnected decrease sharply after the grain boundary is eroded, leading to great separation of grains.
However, the number of IGC signals is much more than that in [3].
Therefore, it is very possible that different testing methods result in different number of AE signals.
Xu [3] did not explore the AE source due to the low AE activity and poor numbers of signals.

Grain size of NiO and SDC could be estimated from the diffraction peaks according to Scherrer equation expressed as[5]:
Table 1 Cell parameter and grain size of NiO and SDC Sample Cell parameters Volume Average grain size A(×10-1nm) V(×10-3nm3) D(nm) NiO SDC NiO SDC NiO SDC NiO400-SDC400 3.965 5.427 62.4 159.9 30.1 15.6 NiO600-SDC600 3.969 5.428 62.6 160.0 56.5 19.7 NiO800-SDC800 3.969 5.430 62.6 160.1 63.4 44.8 The grain size of NiO powders calcined at 400, 600 and 800℃ is 30.1, 56.5 and 63.4nm, and the size of SDC is 15.6, 19.7 and 44.8 nm.
As shown in Table 1, there is grain growth with calcining temperatures from XRD lines broadening.
Thus, the high performance of this anode seems to be attributable to the increase in the number of active sites at the boundary between Ni, SDC and H2 gas.
As shown schematically, the Ni grains form a skeleton with well-connected SDC grains finely distributed over the Ni grains surfaces.

α-SiC powder grew moderately into plate-shaped grains. β-SiC powder was completely transformed to 6H and subsequently 4H with large grain growth.
Numbers beside circles are relative specimen densities.
The closed circles are the experimental points and the numbers alongside the circles are densities in percentage of a theoretical density, left: α-SiC and right: β-SiC.
This introduced anisotropy in grains and resulted in plate or rod-shaped grain growth.
It is considered that grain growth is driven by surface energy stored in fine grains.

With increasing particle concentration, it is much more fine grain due to increasing the number of nucleation core at 6% TiB2/7075 composites.
It makes TiB2 be good grain refiner of Al alloy.
It was nearly spherical grains under the boundary layer.
The more particles content, the smaller grain size was at the corresponding parts.
Acknowledgements This work was supported by the Scientific Research Staring Foundation of Chongqing University of Technology as Project number 2012ZD12 and Project Supported by Scientific and Technological Research Program of Chongqing Municipal Education Commission (Grant No.

Higher T1 temperature and extended soaking time caused larger grain size, which accompanied with the Ostwald ripening of the grain and led to non-uniformity of grain size distribution.
This was mainly because of the pinning of the grain boundary by MgO as the second phase, which inhibited the grain growth to get grain refinement.
So there were more residual pores in the grain, and the grain heterogeneity was obvious.
With the increase of the soaking time, it could be seen from Fig.5 (b) and Fig.5 (c) that the small grains were gradually disappeared and the number of the grain with larger size increased, which also proved that the Ostwald ripening phenomenon occurred in the long soaking time.
The grain boundary was pinned by MgO as the second phase, resulting in hindrance of grain growth and grain refinement

During thermal cycling of titanium with an initial superheated structure, thermal stresses after a certain number of cycles can lead to intragranular plastic deformation, and subsequent recrystallization annealing lead to grain refinement [17, 18].
The number of TCT cycles varied from 1 to 50.
Grain refinement occurs after the first cycle of the TCT (dnom. = 700 microns).
With an increase in the number of cycles, a grain decrease corresponds to an increase in the fatigue limit, which reaches a maximum value (σ-1 = 220-230 MPa) after 10-15 cycles of TCT (dnom. = 245-219 microns).
In our case, the fatigue limit reaches this level with a decrease in the grain size by ~ 3.3 times, which is possibly determined not only by the grain size itself, but also by the method of its production and, in particular, the formation of subgrains with grain-boundary angle in several degrees at the optimal number of TCT cycles, which serve as an additional obstacle to the spread of plastic deformation [24].

�-fibre grains (ND-fibre grains) are, in general terms, more fragmented than �-fibre grains (RD-fibre grains).
This technique enables the orientation of deformation bands, the misorientation across them, the orientation of the new recrystallized grains and the misorientation of those grains with the adjacent matrix grains to be determined.
In zones 3 and 4 a great number of low angle boundaries (<15°) parallel to RD originate, which intersect with the microbands running perpendicular, as can be seen in the image quality map.
The orientations of the recrystallized grains numbered from 1 to 9 in the figure and the misorientation angle/axis with respect to neighboring zones are gathered in Fig. 3-c.
Conf. on Rex. and Grain Growth, Trans.

Crack propagation behaviors in grain, effect of Schmid factor, propagation cross the grain or phase boundaries have been discussed.
The number of crack branches increase with increasing applied stress intensity factor range DK.
The result also shows that fatigue crack branching occurs mainly inside grains, and the number of crack branches seems also higher in the austenitic phase than in the ferritic phase.
Fig. 6a shows the main crack length versus the number of loading cycles.
Crack length versus number of loading cycles.