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We discuss the role of small grains in grain size analysis and derive from the shape of grain boundaries the acting driving forces for grain boundary migration.
Fig. 1: Section of a LASM image of the NEEM ice core (depth: 322 m) – Note the high number of sub-grain boundaries (white arrows) in the vicinity of the air bubble in the upper right corner.
Whether there is normal grain growth (nucleation of new grains is negligible) or dynamic grain growth with a significant contribution of small grains caused by nucleation of new grains is an important aspect as presently normal grain growth is assumed to be the predominant growing mode.
To include small grains affects the mean grain size.
Fig. 2: Profile of mean grain size for different grain size fraction (area filled by grains larger than lower cut-off): 80% (red +), 90% (green *), 95% (blue o) largest grains and all grains (orange x).

In recent years a number of different experimental methodologies have emerged for the study of such microstructures in terms of the individual grains, non-destructively and in three dimensions.
These techniques are generally referred to by the term "grain tracking".
Such techniques may be used to produce 3D maps of grain orientation, to study the dynamics of grain nucleation and growth during annealing, or to measure elastic strain tensors on a grain-by-grain basis.
The grain mapper.
The mapper is designed to work in a number of different modes, depending on the type of measurement.

Unfortunate accidents as well as the rising number of terrorist attacks in urban infrastructures have influenced the increasing number of "accidents" related to fires and consequent damage not only to concrete buildings [1].
The concrete with designation B contained aggregate grain size 8/16 and 11/22 mm, while the concrete with designation C contained coarse aggregate with the grain size of only 4/8 mm.
The number of AE events indicates the probable number of newly created cracks and other defects, and the duration of the AE signal indicates the influence of the quality of the internal structure on the propagation of the mechanical wave.
The acoustic emission method revealed that concrete B exhibits a higher number of AE events, which is again probably due to the negative impact of the higher grain size of the aggregate.
This is similarly true when analysing the parameters of the AE signals where the higher grain size of the aggregate appears to be disadvantageous because the higher number of AE events probably means the formation of a higher number of micro-cracks in the internal structure of the concrete.

The initial bonding between several particles becomes the combination of a number of particles, so the examined results at macro level display area shrinkage ratio enlarging and metallization happening, at micro level quantities of bonding boundaries evolve into symmetrical boundaries as networks which are not continuous and incomplete.
From 1833K to 1953K, a great many recrystal grains come into being, at this time, the new grains’ sizes are very small, impurity such as O is swept away by hydrogen from grain boundaries.
At 2073K, the grains grow up quickly and the bending three branches grain boundaries become smooth, the bigger grains devour the smaller ones, two or more grains combine together into a big one, during the process, the porosities in three branches grain boundaries are closed into big grains.
The porosities in grain boundaries disappear, but the porosities inside of grains remain when the grains around three branches boundaries join into a big grain, at this time, the three branches grain boundaries disappear.
Acknowledgements This work was financially supported by the Shaanxi ‘13115’ Science and Technology Innovation Project (project number: 2008ZDKG-41) and the experiment was carried out under the help of JDC Technology Centre.

Also, the upward trend in monolithic construction is due to a number of technical and economic advantages: relatively low investment in the production base; lower in comparison with prefabricated structures, material consumption and labor costs and high performance [1, 2, 3].
In particular, the improvement of the grains shape by removing sharp and protruding corners can be achieved by rolling.
Removal of large open pores and cavities on the surface of aggregate grains, leading to cement overconsumption in concrete can be carried out by melting the surface of the grains; increasing the uniformity of grains in terms of strength and bulk density can be achieved by separation.
It should be noted that porous aggregates have a number of advantages: they have a developed rough surface, good adhesion to cement stone, the dust-like part is active with respect to cement, and porous differences are capable of creating self-vacuuming effect[6].
Strength Characteristics of Fine-Grained Lightweight Concrete Based on Tuff Waste At this point in time, there are a large number of formulas for predicting the compressive strength (cube strength) on various porous aggregates, depending on technological factors.

Fig. 10- Variation of the hardness as a function of ECAP pass number.
Fig. 11- Variation of the yield stress as a function of ECAP pass number.
Fig. 12- Variation of dislocation density as a function of ECAP pass number.
Fig. 13- Variation of average boundary spacing as a function of ECAP pass number.
Fig. 14 - The calculated and experimentally measured flow stress as a function of the pass number.

Introduction It is well known that grain refinement improves both strength and toughness simultaneously in polycrystalline materials.
So, the number of nuclei for recrystallization [4] is larger in the reversed austenite than the original austenite, resulting in the smaller recrystallized austenite grain size in the initial martensite structure.
(2) The recrystallized austenite grain size is much smaller in the start structure of martensite than the original austenite
Mould: Recrystallization and Grain growth in Metals (A Haisted Press book, 1976), p. 62 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 original austenite martensite Grain size (§-) Reduction of thickness (%) Fig. 6 Relation between the recrystallized austenite grain size and the initial hardness for the two structures of Fe32%Ni alloy.
Fig. 5 Relation between recrystallized austenite grain size and reduction of thickness in the two start structures of Fe32%Ni alloy. 58 59 60 61 62 63 64 65 66 67 10 20 30 40 50 60 70 Grain size (§-) Hardness (HR-15N) Original austenite Martensite

Recent Advances and Unsolved Problems of Grain Boundary Diffusion Sergiy V.
Some unresolved problems of grain boundary diffusion – restrictions of Fisher-Gibbs model, refinement of the conditions for B- and C-regimes, relation between segregation (s) and enrichment (b) coefficients, grain boundary width, non-linear segregation effects on grain boundary diffusion – are discussed.
Grain boundary (GB) diffusion measurements are very sensitive to the structural state of GBs.
Grain boundary self-diffusion of Cu [13] is plotted by thick dashed (the B kinetics) and solid (the C kinetics) lines.
Conclusion A critical consideration of the present state of the art of GB diffusion gives rise to the conclusion that there still exist a large number of “hot” unresolved problems, which demands both experimental and theoretical (including computational) efforts

The Influence of Quenching Baths on Grain Boundary Wetting Transition in Sn-25 at% In alloy C.
The wetting behavior of grain boundaries is affected by temperature, pressure and misorientation of grain boundaries.
However, the influence of quenching baths on liquid state grain boundary wetting is rarely reported.
It is pointed out that a proper quenching bath is necessary for preserving the initial microstructure of grain boundary wetting.
Conclusions The grain boundary wetting behavior of the Sn-25 at.-% In alloy quenched in different baths was investigated.

Grain refinement (with 0.06Ti) was also found to be beneficial to the elimination of hot tearing.
A., “The Columnar to Equiaxed Transition in Horizontal Direct Chill Cast Magnesium Alloy AZ91,” Light Metals, 911-917 (2001). ] noted that the grain refined alloys in their study formed equiaxed-dendritic grains, and gained resistance to hot tearing with moderate additions of grain refiner.
It is noticeable that a small number of dendrites exist in the microstructures of the casting produced without refiner.
With grain refinement, the grains are finer and more globular, with essentially no dendrites present.
One reason for the better performance of the grain refined material might be because fine grains are more ductile than the coarse grains, and therefore, the fine-grained material is free to compensate for strains by movement of both liquid and solid.