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The optimized relaxing time on grain refinement is 60 s.
The linear intercept method was used to measure mean austenite grain diameters.
The austenite grain size becomes smaller with the decrease of reheating temperature.
A small grain sized austenite has a relatively large number density of grain boundary nucleation sites so bainite dominates the microstructure, whereas a relatively large number density of intragranular nucleation sites leads to a microstructure consisting of predominant acicular ferrite [13].
It is therefore proposed that lath-like or plate-like acicular ferrite grains formed earlier effectively divide prior austenite grains into smaller and separate regions.

The result shows that the Al-3Ti-0.5B master alloy which was prepared by adding mixture of Ti sponge and KBF4 power into molten aluminum contains a large number of granular TiB2 phase and blocky TiAl3 phase.
Addition of grain refiners is the most common and effective method for refining the grain structure during the solidification process [1-3].
Compared with B alloy, the number of TiB2 particles in A alloy is more.
Figure 5.a) shows that commercial purity Al without grain refiner exhibits coarse equiaxed grains and columnar grains.
The macrostructure of Al is composed of fine equiaxed grains after the addition of grain refiner as shown in Figure 5.b) and Figure 5.c) respectively.

The fibrous grains are aligned close to the billets extrusion direction.
Showing; the grain sizes obtained, using the mean linear intercept λx parallel and λy perpendicular to the main direction of alignment, grain aspect ratio, equivalent circular diameter (ECD) grain size after grain reconstruction from the EBSD data, the standard deviation of the ECD grain size distributions normalised with respect to the mean diameter (σSD/dm), the percentage of HAGB area, and the mean boundary misorientations.
Overall, this leads to a slightly larger average ECD grain size than for Route A and a grain aspect ratio close to one (Table 1).
The average 'grain sizes' determined in table 1 for this alloy are therefore somewhat misleading, as they are dominated by the larger numbers of small grains present, which are particularly fine in the case of the 90° die.
Altering the die angle from 120 to 90°, changes the ideal shear strain per extrusion cycle from 1.15 to 2, but reduces the total number of cycles to obtain the same strain (from 15 to 9 in this case).

The grain boundary microstructure ( the type, the frequency of grain boundaries and the connectivity of different type of grain boundaries ) was analyzed by SEM-EBSP-OIM for all the specimens.
The initial grain structure is drawn in red lines.
It is reasonable to imagine that the grain boundary connectivity may control the grain growth through the interaction between initially existed grain boundaries and newly formed interphase boundaries during phase transformation.
As shown in Figure 4, significant abnormal grain growth was observed and the magnitude of abnormal grain growth increased with increasing the number of cycling.
The grain size of abnormally grown grains was almost ten times larger than the initial grain size ( d0 =59-65µm).

Grain sizes were measured by intercept method.
When bubbles collapse acoustic streaming develops in the melt, distributing the nuclei into the surrounding liquid producing a significant number of nuclei in the molten alloy, thus promoting heterogeneous nucleation.
When cavitation develops, the shock waves generated by bubbles collapse lead to fragmentation of dendritic cells in the mushy zone, which are re-distributed throughout the melt by acoustic streaming, increasing the number of solidification nuclei.
So the turning point of grain size is 660 ºC.
And because of the high pressure pulses caused by the ultrasonic cavitation, the wettablity of large number of impurity particles, such as Al2O3 based intermetallic particles, will be improved by eliminating the gas absorbed on the particles and fill the melt in the micro cracks of the particles.

Grain size measurements were performed using the lineal intercept method according to ASTM standard E112 88, and more than 40 intercepts were counted for each grain size determination.
The initial grain size of as-cast AZ91 magnesium alloy was about 71 µm (Fig. 2).
Fig. 6 shows grain size as a function of calcium concentration.
These intermetallics prevent the grain growth [12, 13].
Initial grain size of as-cast AZ91 magnesium alloy was about 71 µm.

A new approach to solute effect on grain boundary migration Yan Huang BCAST, Brunel University Kingston Lane, Uxbridge, Middlesex, UB8 3PH UK yan.huang@brunel.ac.uk Keywords: Grain boundary migration, solute drag, activation energy, activation entropy, mobility.
According to this model, grain boundary mobility is dependent on solute concentration rather than migration rate.
The interaction is directly related to a tendency of the solute atoms to segregate to the grain boundaries because they will there cause less elastic stresses than in the interior of a crystal, which forms the basis of the solute effect on grain boundary migration.
For a constant solute and boundary interaction energy (E) and a system containing a number of N boundary atomic sites, the free energy decrease due to solute segregation is -NE Xgb and the mean free energy decrease of each atom is -EXgb, where Xgb is the solute concentration in the boundary.
A new approach, based on the fact that solute segregation reduces the free energy of the grain boundary, is put forward to address the effect of solute on the kinetics of grain boundary migration.

The microstructure of ultrafine-grained steels was analysed before and after nitriding.
HPTD can be used to obtain materials with ultrafine-grained (UFG) structure with mean grain size of less than 1 μm and predominantly large-angle grain boundaries [1-3].
Prior to ion nitriding, samples of martensitic and austenitic steels were treated by heat to obtain a homogeneously grained microstructure.
The presence of a larger number of grain boundaries, vacancies and dislocations in crystalline structure of UFG steel has a stimulating effect on the diffusion of nitrogen, which is confirmed in [9-11].
The presence of a significant number of grains, vacancies and dislocations in the crystalline structure of UFG steels has a stimulating effect on nitrogen diffusion.

The Effect of Copper Content on the Dynamic Grain Growth in AL-Cu-Zr systems K.
An increase in grain size occurred in both materials due to deformation, but this dynamic grain growth (DGG) was much greater in the material with the higher copper content.
An increase in grain size with strain - dynamic grain growth - during hot deformation is a common characteristic reported for a number of materials, and is characterised by a grain growth rate significantly exceeding that which occurs in the absence of plastic strain [5].
This shows that both alloys have undergone dynamic grain growth.
With 2wt% Cu, the initial banded grain structure persisted to large strains and there was relatively little dynamic grain growth.

As the power increased, the size of the nano silver grains increased and the number of grains decreased.
It is apparent that the silver films were composed of compact nano size grains, and the surface shape of the grains varied with the power.
As sputtering power increased, the size of the nano silver grains increased and the number of grains decreased.
As sputtering power increased, some nano grains aggregated to form larger islands, thus the number of the grains appeared to be smaller and their diameter larger.
We measured the number of Staphylococcus aureus bacteria of samples at dilution ratios 10 -1, 10-2 and 10-3.