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Introduction Ultrafine-grained materials (UFG) are widely known as polycrystals having very small grains with average grain size less than ~1 μm [1].
This can be explained by the restricted number of slip systems at low temperatures, and therefore results in poor ductility.
But instead, an island like microstructure (some coarse grains are surrounded by fine grains) was developed after 4 passes.
Grain refinement proceeded with increasing pass numbers and the grain size after 4 passes was much finer (L=100~500 nm) in comparison with the same alloy receiving ECApress without back pressure. 2.
However the maximum texture intensity decreased as the pass number increased from 0 (maximum; 12.9) up to 4 passes (maximum; 7.0~7.1), which indicates that the increase of yield stress is mainly due to the refinement of grain size. 4.

Micrometric Grains.
In average, the more a grain initially deforms, the larger is the number of active slip systems at  max.
This last effect is due to the increasing number of sources that are activated under an increasing stress and to the production of additional sources by a more active cross-slip mechanism.
It also decreases with an increased number of initial sources and with increased cross-slip activity.
In addition, the number of grains, sixteen in the present case, does not need to be extremely large to obtain a reasonably realistic size effect.

The effect of grain size in creep strength and creep rate comes through the grain boundary sliding and grain boundaries as barrier mechanism.
Table 2 shows the solution treatment conditions and grain sizes number.
Heat treatment and average grain sizes.
If the grain size is small, it becomes more dislocations to pile up at grain boundaries and form cavities at the grain boundaries.
Acknowledgements The authors would like to acknowledge Ministry of Education Malaysia and Universiti Teknologi Malaysia (UTM) for provided financial support under grant number Q.J130000. 2524.03H33.

The grains of Fe and S45C were significantly refined to the submicron size range using the HPT process, and the grain sizes were found to decrease with an increased number of turns (N).
In addition, the hardness of HPT-processed Fe was saturated with a further increase in the number of turns owing to the saturation of grain refinement.
A number of SPD processing techniques are now available.
The grain sizes were found to decrease with an increase in the number of turns (N).
The hardness of HPT-processed Fe was saturated with a further increase in the number of turns owing to the saturation of grain refinement.

The Microstructure and Texture of Fine Grain High-Strength IF Steel after Continuous Annealing ZHANG Li-wen1, a ,WANG Zhen-min2,b ,ZHANG Hong-mei ,HOU Jue3,c School of Materials and Engineering ,University of Science and Technology Liao Ning,An shan 114000,China azhanglw1983@163.com Keywords: fine grain high-strength IF steel; texture; holding time; EBSD Abstract: In this paper,the fine grain high-strength IF steel after cold-rolling and continuous annealing was studied.The microstructure under different holding time of fine-grain high strength IF steel was observed by the OM and the TEM technology.
Compared with traditional IF steel, the fine grain high-strength IF steel increase the carbon content and add the appropriate element Nb to fix the solution element(C,N).On one hand, these large number of precipitation of Nb precipitates can effectively prevent the movement of grain boundaries and sub-boundaries, inhibit grain growth and refine the grain.
The grains of 120s and 180s samples have begun to grow, and recrystallized grains have grown up along the rolling direction.
The grains of tested steel are largest and evenly in 120s.
Therefore, the optimal holding time is 120s for the fine grain high-strength IF steel after continuous annealing.

The method of grain refinement is described which is used to obtain titanium and zirconium base alloys in an ultra-fine grain state.
The microdiffraction pattern contains a great number of reflections of different intensities that are arranged in a circle, which is an indication of increasing misorientation angles at the grain boundaries (Fig. 2a).
However, the original coarse grain counterpart has plasticity, which is almost twice that of the ultra-fine grain counterpart (cf. 15% and 8.5%, respectively).
The work hardening stages observed for the test samples of titanium and zirconium, are found to differ in number.
Otherwise, the ultra-fine grain zirconium counterpart has the same mode of fracture as the ultra-fine grain titanium counterpart.

Influence the number of passes through CONFORM machine on thermal stability was study by horizontal dilatometer and heat-flux calorimeter.
They are used for achieving grain refinement to the nano-scale, with the resulting grain size between 100 and 400 nm.
The grain size in this specimen was 1.4 µm.
The resulting grains are equiaxed.
Grain coarsening kinetics In the course of the isothermal annealing experiment, normal grain growth took place.

Abrasive Grain Models.
Thus, the value of the grain volume has an influence on the distribution and consequently on the number of grains in the grinding wheel surface [5], which follows from Eq. 1 [7].
The number of grains in a defined volume NV can be calculated from the abrasive concentration C, the density of the cutting material ρg and the volume of the abrasive grain Vg.
While using the same grain size, the shape of the abrasive grain has significant effects on the grain's volume and the number of grains in a defined volume.
The distribution model and the concentration characterize the number of active cutting edges.

These particles are termed as abrasive grains at a large number and their size and distribution are very random and therefore it makes the grinding process a very complex machining process to be studied.
Workpiece Grain 1 Grain 2 Grain 3 (a) (b) Fig. 1 The multiple-grain cutting model In high deformation zones close to contact zone between the workpiece and the grains, the SPH method was implemented in the central part of the workpiece as a cuboid of 160 μm × 120 μm × 20 μm with fully taking advantage of this method.
(a) (b) Fig. 3 Total force and chip formation at each grain from 3-D simulations In the model, Grain 2 was arranged right to Grain 1 while Grain 3 was just behind these other two.
Grains 1 and 2 have much closer results during the cutting process compared to Grain 3 since these two grains are located in the upstream.
Pile-ups generated by Grains 1 and 2 were found ahead of Grain 1 while the softening was decreased, thus the cutting force of grain1 became larger than those from Grains 2 and 3.

Cavitation behavior during superplastic flow of ultra-fine grained (UFG) Ti-6Al-4V alloy was established with the variation of grain size and misorientation.
Distinct colors indicate the orientation of each grain.
Regardless of the number of ECAP deformation in this study, most alpha-phase and beta-phase grains were considerably refined and fragmented to ≈ 0.3 µm in diameter without changing volume fraction of each phase.
Firstly, the size, number, distribution, aspect ratio and area fraction of cavities decreased in materials with finer grain size and more distinctive misorientation.
proportional to the grain size [5].