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Introduction With the development of Northwest China inland construction, the number of road and railway construction projects increases gradually, and many routes need to go through Gobi area.
In the loading process, the coarse-grained soil deformation mainly results from the relative movement between adjacent grains and grain rearrangement.
Grain analysis.
In dry state, the coarse grains are surrounded by a large number of fine grains, which are in floc-like aggregations, with random shape, size and geometric features.
Meanwhile, the decreasing coarse grains and increasing fine grains in grain group lead to the re-arrangement and rolling of coarse-grained soil in Gobi region under the force of external load until the balance achieved by internal soil force and external load causing the sudden settlement of coarse-grained soil.

Experimental points are shown for both the unprocessed (coarse-grained) and for the ECAPed materials.
The theoretical rates using dECAP will be marked by simple number (e.g. 1) while a numbering with asterisk (e.g. 1*) will be used for the rates corresponding to dCREEP in Fig. 1.
Further, for n ³ 4 creep is known to occur by diffusion-controlled movement of dislocations within grains and/or along grain boundaries (grain boundary sliding).
Supposing that grain boundary sliding is controlled by grain boundary diffusion, which is assumed to be about 0.7 times that for lattice self-diffusion, the presented results give support to the assumption that grain boundary sliding may be increasingly important in the ECAP aluminium and copper at low applied stresses (see Fig.2a).
Diffusion creep is not important because the ultrafine-grained microstructures are unstable at creep temperature and the grains grow during creep sufficiently to preclude any significant contribution from diffusion creep.

SAD patterns of the alloys processed by 3 or 4 ARB cycles show increased number of diffused spots.
As the number of the ARB cycle increases, the grain boundaries became better defined and sharp; the number of poorly defined boundaries, the extinction contours, and the dislocation density inside the grains decreased.
Sliding wear rates of the ARB-processed Al alloys are plotted against number of ARB cycles in Figs. 3 and 4.
Variation of wear rate of the ARB processed 5052 Al alloy as a function of number of ARB cycle. 0 1 2 3 4 5 6 7 0 10 20 30 40 50 Wear Rate (1x10 -13 m 3 /m) Number of Cycle Applied Load : 1N Applied Load : 2N Applied Load : 3N Applied Load : 4N Fig. 4.
Variation of wear rate of the ARB processed 5083 Al alloy as a function of number of ARB cycle.

As a measure of austenite grain size the mean chord length of austenite grains was assumed.
In this test the value of c2 was calculated using equation: (3) where ni and nei are the experimental and expected numbers of grains in the i-th category of chord lengths.
The variable c2 has a distribution with a degree of freedom equal s=k-r-1, where k is the number of categories and r is number of parameters describing distributions.
For freedom degrees number s=12 the critical value is equal c20,05=21,026 [13].
At temperature 1100oC there is below 10 % of grains with austenite grain chord lengths over 100 mm in B-V2 melt and 40 % in melt B-V1.

av.randle@swansea.ac.uk, bm.p.coleman@swansea.ac.uk Keywords: Grain boundary engineering, annealing twinning, grain growth control.
Grain Size Distributions in Grain Boundary Engineered Microstructures Table 1 is a collation of average grain sizes which have been included in a selection of recent reported GBE investigations.
Average grain size taken from recent GBE investigations Material Average Grain size Source (nm) Copper 12 Randle V. and Coleman M.
The crystallite size is hence smaller than the grain size.
The crystallite size was related to the number of Σ3 boundaries present.

With a growing number of passes, the size of subgrains observed at ∆ = 2o is not much dependent on N, whereas the influence of N upon the grain size is much more pronounced at higher values of ∆.
The observed ratios Ev(∆=15 o )/Ev(∆=2 o), i.e. the mean number of subgrains with boundaries mutually disoriented by more than 2 o to the mean number of conventionally defined grains, are between 30÷100 and 10÷30 at N = 2 and 4, resp., and 4 at and 8, 12 (the higher ratios at N = 2, 4 correspond to as pressed material and there is no substantial difference between the as pressed and annealed material after N = 8, 12).
In homogeneous systems of grains and subgrains 0.55 ≤ CV a < 1, in mildly non-homogeneous systems is CV a lower than 2 and higher values are typical for systems with multimodal grain size distributions with a great number of small (sub)grains encircled by or included in extremely large (sub)grains which is the case of the material after N = 2 and partly also after N = 4 (for examples of 3D grain systems see http://fyzika.ft.utb.cz/voronoi/).
They decrease with the growing number N, increase with ∆ and are lower in annealed specimens.
With increasing number of ECAP passes, a pronounced grain refinement takes place and simultaneously also the homogeneity and isotropy of the grain and subgrain structures improve. 2.

The uniformity of the β grain size is determined by a grain ratio η = A1/A, where A1 is the number of the grains of which sizes are in the range of 0.6 ~ 1.4 D (D is the average β grain size) and A is the total number of the measured β grains.
Thus, the average grain size increases with the holding times, and at any particular instant there will exist a range of grain sizes.
The high value means the more high uniformity of the β grain size and the low value means the non-uniform β grain size.
That means that, the driving force for grain growth is a reduction in the energy which is stored in the material in the form of grain boundaries.
Generally it is said that the kinetics of grain growth are not influenced by the prior grain size (D0) and at longer time D0 term is negligible.

Analytical Grain Size Distribution Grain microstructures obtained by curvature-driven normal grain growth can be characterised a mean grain size of the ensemble of grains changing with time according to a parabolic growth law.
The temporal development of the grain size for 17 different randomly picked grains is shown in Figure 2.
Figure 2: Temporal development of the grain size for simulation data and Eq. (7): a – randomly selected grains very well represented by Eqs. (7); b – grains showing only weak agreement with Eqs. (7).
Stochastic Motion of Individual Grains While the grain microstructure shows coarsening and the number of grains is reduced, stochastic changes in the lengths of the triple lines and, hence, a fluctuating quadruple point distance can be observed.
For reasons of a better illustration the 3D coordinates are plotted in projection in the y-z-plane and the associated x-coordinates are marked by numbers.

Microstructural barriers against fatigue crack growth Alain Franz Knorr1,a, Michael Marx1,b 1Institute of Materials Science and Methods, Saarland University, Saarbruecken, Germany aa.knorr@matsci.uni-sb.de, bm.marx@matsci.uni-sb.de Keywords: Fatigue, Small cracks, Grain boundaries, FIB-tomography Abstract Fatigue induced fracture is the number one reason for failure of technical systems.
Sometimes the cracks stop completely for a large number of cycles resulting in an additional number of life time cycles.
Afterwards fatigue crack growth is monitored by replica technique; images of the surface are taken after a constant number of load cycles.
This can be repeated for different crystallographic orientations of the two participating grains, the initial grain and the neighbouring grain.
In fact grain A with the initial notch is surrounded by grain B.

Grain Boundary Engineering: progress and Challenges Weiguo Wang 1, a 1 Department of metallic materials, School of mechanical engineering, Shandong university of technology, Zibo 255049, PR China a email:wang.wei.guo@163.com, Keywords: Grain boundary engineering; Grain boundary character distribution; CSL boundary; .
The resistance of grain boundary engineered materials to grain boundary degradation have been improved dramatically, and some GBE processed metals have been put into use.
Finally, the fourth, which is frequently used in GBE field [21,26], is a iterative process of low-strain low-temperature long-time anneal or intermediate-strain high-temperature short-time anneal and usually, the number of iteration is 2 -7.
These data are all given based on number or length fraction of low ∑-CSL boundaries out of the total interfaces.
Though it might be meaningful to pursuing high fraction of SBs, it must be pointed out higher number or length fraction of SBs doesn't mean the better optimization of GBCD.