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Within each austenite grain there is a microstructure, and this microstructure was investigated using a color etching technique to reveal the eutectic cells and the dendritic network.
The primary austenite grains nucleate as either columnar or equiaxed crystals depending on preferential nucleation sites and heat removal.
At the same time the number of whole cells in a field of view was counted.
This is the result of the increased number of nucleation sites.
Number of eutectic cells versus eutectic cell size.

Ultrafine-grained Ti6Al4V were obtained by high energy ball milling and spark plasma sintering [3].
They have accomplished the production of powder particles consisting of a shell and core hybrid microstructure, meaning a shell structure with nano-grains and a core structure with work-hardened coarse grains [12].
Additional experiments are needed to determine the optimal number of milling hours after which the amorphous state with the maximum exothermic reaction is obtained translating this into lowering the energy required for melting/sintering.
Long et al., High-strength Ti–6Al–4V with ultrafine-grained structure fabricated by high energy ball milling and spark plasma sintering, Mater.
Saitova, Cyclic deformation behavior and fatigue lives of ultrafine-grained Ti-6AL-4V ELI alloy for medical use, Int J Fatigue 31 (2009) 322–331 [9] O.

The cold rolled steel structure consists of large elongated grains along the rolling direction(RD), with an average grain size of 27μm.
The annealing at 450°C after 4500sec, no strain free grains are observed by optical microscopy image Fig.2(a), However, the sub grain structure is identified by TEM images as shown in Fig.2(b).
With increasing annealing temperature to 620°C, the strain-free grains are nucleted after 20sec in deformed matrix(arrow mark shown nucleated grains in Fig.3(a)), and the partial cluesters of recrystallised grains are observed at 90sec as shown in Fig.3(b).
Finally equiaxed and fully recrystallised grains are observed after annealing at 620°C for 1800sec with an average grain size of 11μm.
At 620°C, observed nucleated and large number of strain free grains(Recrystallized) correspond to stagnant coercivity (Hc) and increasing MBE signal with the decrease of mechanical hardness.

Adopting ultrasonic composite processing we describe the influence of different processing parameters and grain size of diamond wheel on the grinding forces and surface roughness.
Nano ceramics materials obtained by nano technology are that their crystal grain, grain boundary and their bonding are at the nano level(1-100nm) among the microstructure of ceramics materials.
Because of the refinement of nano ceramics grain, the number of their grain boundary increases greatly to increase the intensity, malleability and superplasticity of materials greatly and overcome many shortages of engineering ceramics and have the great effect on the mechanical property, electrical performance, thermal performance, magnetic performance and optical performance of materials[1-2].
Because the nano ZrO2 ceramics has the larger superplastic property than the general hard brittle material, its deformation mechanism is that grain boundary slip, particles rearrange and the fracture way is mostly transgranular fracture.
(such as geometric parameters of cutting lip, the grinding speed, the cutting-in of grain and grinding fluid etc) The other symbols the same with formula (1).

Fig. 4 Processing map of experimental steel at a strain of 0.9; the numbers represent the percent efficiency of power dissipation ; Shaded region corresponds to good processing domain.
Numerous DRX grains nucleate at the boundaries and intern of the austenite grain at 900℃ but mixed crystal structure exists as seen in Fig. 5a.
It can be conclude that with the increasing deformation temperature at the same strain rate, the volume fraction of ferrite had an obviously increase and the original grains were replaced by DRX grains completely which is because the higher deformation temperature drives the dislocations to climb or slip on the grain boundary more powerfully.
It is clearly that the banded ferrite have been broken, and the grain size of the austenite increased at the same time at lower strain rate.
Coupled strengthening in a medium manganese lightweight steel with an inhomogeneously grained structure of austenite[J].

The grain morphology of Si3N4 was reported to be strongly influenced by the distribution of the SiC nanoprecipitates.
The microstructure of the V-SiCN material consists of α-Si3N4 equiaxed grains (mean grain size ~ 200 nm) and elongated β-Si3N4 grains embedded in a glassy phase forming continuous intergranular films and pockets at multi-grains junctions (Fig. 2-a).
The O-SiCN material has a finer microstructure with equiaxed β-Si3N4 grains (mean grain size ~ 60 nm) and coarser Si2N2O grains with irregular shapes (Fig. 2-b).
In the case of O-SiCN, the smaller grain size should lead to an even more important deformation.
However, on one hand the oxygen content of the glassy phase is less than in the HMDS material and, on the other hand, for a given amount of glassy phase, the large increase of the total grain surface area might result in an important number of grain boundaries being free of glassy films.

A quantitative metallography study was conducted on the partially softened structure to investigate the number density of recrystallized grains and to verify the indirect measurements of the fraction recrystallized calculated based on the mechanical properties.
The grain size was measured according to the ASTM E112-88 standard (Jeffries' method).
For this method, grain sizes were calculated from micrographs taken at approximately 480X magnification such that each micrograph contained at least 250 grains.
Table 3 - Grain size and yield stress values for the starting IC and CC hot band.
All the recrystallized materials exhibited an equiaxed grain structure.

Scoria is accretion formed by packing of particles, mainly coarse grains with average diameter, rarely fine grains.
According to the experimentation results of Wulanhada volcano along state highway 208, grains of 15mm~60mm diameter accounts for 70%, and grains with a diameter less than 0.075mm only accounts for 2%.
After the compaction, the grains have changed evidently with a reduced void in general between grains and an increased grain distribution range with high porosity inside.
Regarding construction site control, water replacement method can be adopted as an assisting method, and number of roller passes as the control index.
Scoria is a material of grains with slight cohesion between the grains, and furthermore the side slope is easily loosed impacted by human activities and animal and water.

Estimation of the grain size change in steel from acoustic images (c) under multi-cycle loading (the highest probability of crack formation at dg ~30 microns, st. 16GS, number of cycles Nc).
As a result of deformation effects on metal samples, areas with extreme values of a number of characteristics, or areas of limit states (LS), were formed in a number of their areas.
Additional use of the built-in optimization functions of the MS Excel Application, for example, " Search for a solution”, allowed to identify the number of load cycles (Nc) for which the grain size is maximum (Fig. 4c).
At the same time, the change in grain size can reach 45-65%, and the dangerous interval of the number of cycles lies from ~ 4 to 4.5 thousand.
Such images allow us to calculate the amount of grain dispersion and the degree of anisotropy of the material.

A Numerical Study of Combined Rate, Size and Thermal Effects on the Responses of Ultrananocrystalline Diamond Luming Shen 1 and Zhen Chen2 1 Department of Civil Engineering, Monash University, Victoria 3800, Australia 2 Department of Civil and Environmental Engineering, University of Missouri-Columbia, Columbia, MO 65211-2200, USA 1 Luming.Shen@eng.monash.edu.au, 2ChenZh@missouri.edu Keywords: Ultrananocrystalline Diamond; Rate Effect, Size Effect, Thermal Effect, Molecular Dynamics, Grain Boundary; Abstract: To better understand the responses of ultrananocrystalline diamond (UNCD) under extreme working conditions, a numerical study is performed to investigate the size, loading rate and thermal effects on the material properties of UNCD films.
The responses of the resulting UNCD films with various grain sizes are then investigated by applying displacement-controlled tensile loading with different rates and temperatures in the MD simulations.
With the optimization in the MD self-assembly process, these two diamond crystallites are firmly connected through a grain boundary (GB) which is assumed to represent a typical UNCD GB since each diamond crystallite is grown by the KMC method based on the UNCD growth mechanism.
At each atom, the local stress tensor is defined to be ij N ij ij i i n Ω rf β ⊗ −= ∑> 1 (1) where i refers to the atom considered and j refers to the neighboring atom, rij is the position vector between atoms i and j, Nn is the number of neighboring atoms surrounding atom i, Ωi is the representative volume of atom i, and fij is the force vector on atom i due to atom j.
The global stress tensor is then given by ∑= * * 1 N i i N β σ (2) where N* represents the total number of atoms in a representative volume.