Search results

Austenite grains did not coarsen for 60 s, see Fig. 1a-c.
The effect of prior deformation is to accelerate recrystallization nucleation kinetics, which can be related to the number density of austenite grains.
Effect of solute niobium on coarsening kinetics of austenite: The driving force for grain coarsening is the reduction in surface energy associated with grain boundary, expressed as: G=2γR (1) The boundary mobility for plain C-Mn steel as determined by Zhou et al. [4] is: MC-Mn= 0.192Tt exp-20,837Tt m4/J s (2) This is modified to incorporate solute drag effect which was modeled using Cahn’s equation [5] Mgbt=1MC-Mn+αCNb-1 m4/J s where, α=δNvkBT2EbDsinhEbkBT-EbkBT (3) MC-Mn and CNb refer to the intrinsic grain boundary mobility of the C-Mn steel and the concentration of Nb in solution respectively, δ is the grain boundary width ∼1 nm, Nv is the number of atoms per unit volume, Eb is the solute-boundary binding energy (20 kJ/mol) and D is the trans-interface boundary diffusion which is equal to twice the bulk diffusion coefficient of Nb in austenite [6].
Table-1: Effect of austenite grain size and % reduction below temperature of no recrystallization (TNR) on Sv factor and ferrite grain size.
Thus, the key to obtaining target ferrite grain size in API –X-70 in high Nb microalloyed steel in compact strip rolling is to refine the austenite grain size by static recrystallization and take advantage of solute drag due to high niobium to prevent grain coarsening of grain refined austenite as in OHTP process.

The objective of this work is to discriminate single corn kernel and some broken kernels, which are difficult to achieve on the existing machinery and equipment, especially for the counted number and quality inspection process.
ENg ，W.F.Wilcke used three-layer neural network to research the detection techniques of grain damage and moldy maize grain [2]; in 2008, Shi Zhixing, Cheng Hong etc.
Based on the Matlab environment, through statistical analysis of a large number of corn kernels image, we can extracted a threshold of Area from the image [7].
Type 0 for broken kernel, 1 full grain, large amounts of data were normalized to train the model.
It was concluded that this may be used for variety and quality testing equipment for masses of grain.

Compared these inverse pole figures, we can see that the number of grains with <111> pole orientation was larger in the ND in samples warm-rolled at 700°C, which means that samples warm-rolled at 700°C had more grains with {111} planes oriented to the sheet surface than the samples warm-rolled at 800°C.
The {111}<112> oriented grains had high stored energy, when warm-rolled an 700°C, more stored energy leaded to get more grains with the {111}<112> orientation, at same time, those grains had a small subgrain size, based on the subgrain coarsening theory [5], {111}<112>grains had a high mobility and consumed other orientations during recrystallization annealing, then, the more population of{111}<112>grains orientation were appeared in the samples warm-rolled at 700°C.
Frequency (%) Low angle CSL High angle Grain boundary type Fig.3.
Population of grain boundary types in two samples warm-rolled at 800°C and 700°C, respectively Fig. 3 gave the population of grain boundary types in two samples.
Grain boundaries were general classed into three main types: low angle, high angle and coincidence site lattice (CSL), CSL was a special type of high angle grain boundary type and usually expressed by ∑ value.

Accordingly, in order to distinguish the three types of grains in three-phase microstructure, just assume the total number of order parameters is p.
Only (p-2) number of order parameters is evolved during simulation to represent the matrix grains.
The Modified Three-dimensional Simulation Algorithm In some former works, a large number of order parameters are involved to avoid coalescence of grains during evolution.
Kill and Chen [13] proposed a way called reassignment algorithm to reduce the number of order parameters without coalescence of grains.
Computer simulation of the domain dynamics of a quenched system with a large number of nonconserved order parameters: The grain-growth kinetics, Phys.

In this table, α1 means typical size of tungsten carbide grains used as a raw material and α2 means typical size of tungsten carbide grains grown in sintering.
The number of fatigue cycles i.e. the number of rotations was determined by multiplying the rotational speed and the time endured.
From this result, for ultrafine grain cemented carbides, it is difficult to say that the fatigue strength depends on the cobalt content and grain size.
(3) The ultrafine grain cemented carbides did not show a trend that the rotating bending fatigue curve depends on cobalt content and tungsten carbide grain size, which had been reported for conventional cemented carbides
Figure 5 SEM observation of fracture surface of drill blank; material A, deflection 91µm, number of revolution 12,000

A structure of layers (flat grains) is observed.
The thickness of separate layers depends on the number of passes, and it is in the range of 150 to 400nm.
As the number of passes increased, the increase of the density of the poles <112> || ND and <110> || ED was observed.
The microstructure and texture evolution in the deformed and recrystallized states were investigated by TEM orientation mapping in a number of samples deformed in 6 passes.
The diameter of the recrystallized grains in the vicinity of LSPPs was only occasionally larger than the average grain size.

Introduction The nanostructured (NS) (< 100 nm) or ultrafine grained (UFG) (<1 µm) materials can result in dramatically improved -or different- properties from conventional grain-size (>1 µm) polycrystalline or single crystal materials of the same chemical composition.
Manufacturing BNMs with least grain growth from initial powders is challenging because of the bottle neck of bottom-up methods using the conventional powder metallurgy of compaction and sintering.
If some unique properties are limited to the finest grain sizes, methods must be found to stabilize the grain size while attaining theoretical density and complete particulate bonding.
The number of initial mesh (4 node isoparametric plane strain element) was 1000.
This number of elements was found to be sufficient to show local deformation of the strain rate insensitive workpieces by calculating with varying the number of elements.

Table 2 Rolling processes of testing steel plate Rolling process Ⅰ stage rolling Ⅱ stage rolling Pass number Total rolling reduction/mm Average reduction ratio of pass /% Pass number Total rolling reduction/mm Average reduction ratio of pass /% Total reduction ratio of last three passes Ⅰ 6 135.716 12.42 6 69.25 15.24 36.01 Ⅱ 5 132.74 14.58 6 69.252 15.25 40.44 The effect of rolling process on microstructure.The picture of metallographic structure at the place where is 1/4 steel plate thickness is shown in figure 1 (a, b).
Research shows [3] that the way to refine crystal grain includes: the elements (such as Nb, V, Ti ) of grain refinement is formed into stable carbonitride to inhibit the growth of crystal grain, control rolling process (rolling temperature, rolling reduction), refine austenite grain, strengthen cooling rate and refine ferritic structure.
The increase of austenite grain boundary area provides more position for ferrite deformed nucleus of austenite, which refines the rolled ferrite grain.
This explains the phenomenon that yield ratio of steel is increased by refined grain, namely, the thinner ferrite grain, the bigger yield ratio.
Research of Steels Grain Refinement [J].

Braginsky et al.[3] extended this model to simulate sintering in a complex powder compact consisting of a large number of particles of arbitrary shape.
Sintering temperature is an important parameter affecting grain growth of ceramic tool material, the mean grain size L can be given by the following equation [4]: (1) where γ is grain boundary energy, A the accommodation probability, Z the average number of atoms per unit area at the grain boundary, Vm the volume of specific mol, Na Avogadro’s number, h Planck’s constant, R the gas constant, Ts absolute sintering temperature, ΔSa the activation entropy, Qa the activation energy, t the real grain growth time, L0 the initial grain size at t = 0.
Lattice sites having the identical Q number are considered as a grain, and a grain boundary segment is defined to lie between sites of different Q number.
Grain growth can be viewed as transition of atoms owning energy, higher temperature means higher energy and faster rate of grain growth.
It can be found that the mean grain size of matrix phase and the number of nano-particles entrapped into the matrix grains all increase with an increment in sintering temperature in the same simulation time, indicating that higher sintering temperature is beneficial to grain growth and the formation of intragranular-type microstructure.

However, the widespread application of the Mg alloys is seriously restricted by two principal drawbacks: low ductility at room temperature due to limited number of available slip systems and poor weldability.
Therefore, a number of research efforts were undertaken recently in an attempt to clarify this issue [6-10].
The microstructure consists of low-aspect ratio grains with an average grain size of ~19 µm.
Formation of the fine-grains along the original grain boundaries significantly decreases the average grain size and somewhat reduces the LAB fraction in Region 4 (Table 1).
This also may give rise to the fine equiaxed grains along the original grain boundaries.