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In more recent years, the culmination of a number of substantial worldwide research programmes have shown that realisation of a submicron (<1µm) grain size is now achievable through hot rolling.
%C steel with increase in ECAE deformation 0 1 2 3 4 0 1 2 3 4 Strain (von Mises) Boundary Spacing (µm) 0 20 40 60 80 100 0 1 2 3 4 5 6 Number of ECAE passes Percentage HAGB (%) Grain Width % HAGB 0 200 400 600 800 1000 1200 1400 0 1 2 3 4 5 Number of ECAE passes Tensile Strength (MPa) 0 5 10 15 20 25 30 35 Elongation (%) 0.2%PS (MPa) UTS ElongationSummary Efforts to produce a two-phase ultra-fine grained structure in high carbon (0.6-1.2wt.%) steels through innovative deformation have proved successful.
Slow grain refinement observed in the 0.6wt.
Dong: Ultra-fine Grained Steels and Properties, International Symposium on Ultrafine Grained Steels (2001), p. 18
Miller: The Ductility of Ultrafine Grained Alloys, Ultrafine-Grain Metals, J.J.

The 500MPa ultra fine grained steel grain size changing rule with heating temperature variation of the peak under air cooling was shown in Fig 3.
From Fig 6 it could be seen that in accordance with hardness, the yield strength and tensile strength of ultra fine grained steel declined with the increase of heating temperature compared with the original state, and the yield strength reached its lowest value at 800°C, this was caused by the decline of residual stress inside the material and pearlite spheroidization, which resulted in yield strength decreasing; however, the tensile strength at 800 actually rose slowly, this was because the yield strength of the material was very low, a large number of plastic deformation took place and resulted in hardening, so the fracture strength did not reach its minimum value; in the heating process above 900°C, ultra fine grained steel grain grew seriously, which decreased strength.
Figures 8 and 9 showed the hardness and grain size of 500MPa ultra fine grained steel HAZ with cooling rate t8/5 = 6s.
Conclusions (1) The crystals of 500MPa ultra fine grained steel at HAZ grew obviously, and the range of the grain coarsening temperature was 1000-1200
Chen, Computer Simulation of Austenite Grain Growth in HAZ of Ultra-Fine Grain Steel. 2002, Beijing university of technology: Beijing

The water-cooled copper mold casting with slope vibration at the temperature near liquidus can obtain Al-7Si-2RE alloy with small homogeneous equiaxed grains, the average grain diameter is 48.3μm, and the average grain roundness is 1.92.
It would lead to produce different conditions of nucleation and grain growth in the solidification process.
The reason lies in two aspects: on the one hand, in the casting process, the slope can make the molten alloy roll while flowing to the mold, which plays a similar role of mechanical agitation; on the other hand, the exist of a certain temperature difference between the slope and molten alloy, makes the contact surface to meet the nucleation conditions of producing a large number of nuclei easily, and these nuclei roll into the melt alloy so as to increase the number of grains.
It can be seen from Fig.4(c) that slope water-cooled copper mold casting with a certain amount of mechanical vibration can further refine the alloy microstructure, and the grains are more rounded in the whole with its number increasing and its size reducing.
The microstructure of Al-7Si-2RE alloy from slope water-cooled copper mold casting with mechanical vibration was small and equiaxed with the average grain diameter of 48.3μm and the average grain roundness of 1.92.

After HPT, the grain size was found to have a mean value about 100 nm for both alloys.
The applied pressure of 6 GPa and number of rotations 20 were used to process the 1570 alloy.
A mean grain size was estimated from TEM dark field measurements in torsion plane over 350 grains from an area situated at the middle of an HPT disc radius.
It is interesting to note that these segregations seem to spread over distances much larger than conventional grain boundary segregations observed along equilibrium grain boundaries.
In addition, dislocations are generated at grain boundaries and move through a grain to be captured by an opposite grain boundary.

A number of these particles show co-precipitates and contain Nb suggesting that NbC co-precipitates at TiN.
Further, a number of Mo-rich particles were observed with a size of approximately 100 nm.
At least 400 grains were measured to quantify the mean EQAD.
These larger grain sizes indicate appreciable grain growth during heating at a rate of 10 °C/s rather than during the brief holding at peak temperature.
The promotion of grain growth above 1150 °C may be related to dissolution of NbC even though no indication of abnormal grain growth was observed.

A number of algorithms and strategies are now being used to solve complex optimization SRM grain design problems, which are used to be treated by classical or heuristic optimization methods[2-4].
On the other side, in the engineering practice, the designing of SRM grain is constrained by a number of performance and structure restrictions, which narrow down the optimizing space remarkably.
The grain regression based on PFCADM is achieved by embedding the regression parameter in the variable defining when modeling grain CAD model, i.e.,.
Thus, the objective and constraint functions from designing variables of sphere slot grain to grain performance parameters is established.
These restrict application on the grain optimization problem.

Al-5Ti-C alloy has a good grain refining capacity for commercially pure aluminum.
The grain refinement experiment was made in the well type resistance furnace.
As we can see from Figure 2 (a), on the Al substrate of Al-5Ti-C alloy are uniformly distributed a large number of strip-like or lump-like substances with the size of about 20 ~ 55μm in length and 8 ~ 12μm in width and small black particles.
After a heat preservation time of 120 minutes, there is a significant difference of the grain size between the top and bottom of the sample, the grains at the top being large, while those at the bottom small, and the closer to the bottom, the finer the grains(See Figure 3 (e)).
When the heat preservation time continues to increase to 120 minutes, a large number of precipitates appear at the bottom of the sample (as shown in Figure 4 (e)).

Simulation model Cellular automata are mathematicl descriptions of physical systems for which space is divided into a great number of individual cells, time is alse discretized.
Table 1 Parameters of the simulation model Cells Number N Orientation S Simulation Step /CAS Particle’s Shape 500×500 1000 2000 circle Results Before considering the evolution of the simulated material, it is useful to examine the behaviour of a single circular grain in the presence of the second phase particles[3].
The slope (n) of their fitting line decreases gradually, this means that n is not a constant number and it decreases with the increase of simulation time when the matrix contains second phase particles.
As the simulation time crease, grain boundaries are pinned, and then the grain growth is inhibited.
In Model B (or Model C), the grain growth has been under way for some time, the grain size has become big.

Cold rolling (CR) was conducted on coarse grained (CG) and ultrafine-grained (UFG) coppers, obtained by 1 and 8 passes in the equal channel angel pressing (ECAP), to investigate the effect of grain size on rolling texture.
Moreover the grain size distribution was fairly heterogeneous, with a small number of grains significantly deformed.
As compared, the average grain size of the UFG copper kept the same, although the grain boundaries became more sharply and straight (Fig. 6(b)).
Summary Coarse-grained and ultra-fine grained coppers, produced by 1 and 8 pass ECAP processing, were applied to exclude the influence of the texture before cold rolling and research on the grain size effect on cold rolling texture.
Valiev, Effect of cold rolling on microstructure and mechanical properties of copper subjected to ECAP with various numbers of passes, Mat.

The shears in one grain are opposite to those in the other grain.
Each grain was discretised into a large number of elements (with 17496 integration points) to effectively capture the complex nature of the plastic fields in the vicinity of the grain boundaries.
Dark lines: grain boundaries.
Grain 2 seems to split into two halves starting from the triple junction with grain 3 and grain 4.
Grain 1 Grain 2 Grain 3 Fig 7 Hypothetical "simple" geometrically admissible strain pattern at a triple junction.