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Saito: Ultrafine Grained Materails II, eds.
Tsuchiya, Ultrafine Grained Materials III, eds.
Hughes: Ultrafine Grained Materials III, eds.
Houbaert: Ultrafine Grained Materials III, eds.
Hughes: Ultrafine Grained Materials III, eds.

The density of the distribution of discrete particles Nv can be calculated from the number of particles observed Np in the volume v analyzed, i.e.,
There is no trace of precipitates in the grains or at grain boundaries.
The Cu-rich particle number density decreases with the aging time at 650°C (see Fig. 5(b)).
However, Cu-rich particles still keep nano-size and distribute homogenously in austenitic grains till 1,000h aging.
Vol. 55 (2006), p. 35 (a) (b) Fig. 5 The change of particle size (a) and its number density (b) of Cu-rich phase for Super304H aged at 650°C

The kinetic undercooling is neglected, so the current model is only valid for growth at low Péclet number (usually Pé<1).
The simulations of AZ91D multi-grain columnar dendrites growth were performed under thermal gradient of 10 K/mm.
Simulation results of multi-grain columnar dendrites growth of AZ91D at the beginning (a), middle (b) and almost final (c) stage.
Multi-grain Growth of Mg-Gd-Y Mg Alloy.
Multi-grain growth simulations of Mg-10Gd-2Y-0.5Zr (wt%) Mg alloy were carried out employing the current model.

In both case, the average grain size of the ferrite was similar and amounts to 11 µm.
The measurement of the number of Barkhausen jumps count was performed with voltage discrimination.
It is also an effect of modification domain structure by grain size, number and strength of pinning points.
Fig. 7 Dependence of BN amplitude as a function of applied stress Fig. 8 Dependence of root mean square value of BN as a function of applied stress Fig. 9 Dependence of number of Barkhausen jumps over 1.04 V as a function of applied stress Fig. 10 Dependence of number of Barkhausen jumps over 1.71 V as a function of applied stress Taking into consideration the aforementioned shift of curves of the first sample, analysis of the number of Barkhausen jumps over different amplitude, allows to state that in samples with bigger grain size relatively dominate jumps with smaller amplitude.
The differences in residual stress value in a product made from S235JGR2 steel with 19 µm grain size, determined on the basis of calibration function prepared at sample with 11 µm grain size can reach 100 MPa.

Refining the prior austenite grain size through repeated heating is a process commonly used to enhance the material’s strength.
A comparison of the prior austenite grain sizes refinement achieved through repeated quenching is shown in Figure 3.
Then we can obtaion the information of Homology such as the Betti numbers b0 and b1.
Here, to characterize the difference of (a) and (b), we show the number of b1.
This work was supported by JSPS KAKENHI Grant Number 24654025.

Small-angle grain boundaries decrease or even disappear.
In recent years, many researchers have done a lot of researches, and find that there are a large number of intermetallic compounds in mixing zone joint organizations [9-10].
Within the grain interior in matrix Al, tangled and high density dislocations can be seen.
Plastic deformation makes the crystal structure to change, resulting in a large number of dislocations showed uneven confusion distribution.
The grain size increased slightly.

In additions, there are a number of impurity elements like Fe, Cu and Si.
The initial microstructure is composed of coarse equiaxed α-Mg grains with α-Mg-Mg17Al12 eutectic phase [24-25] located on grain boundary (Fig.10a2).
However, it indicates that the FZ is a fine grained structure and the HAZ is a coarse grain microstructure.
This result can be attributed to an effect of grain size.
Fig.18c represent a fractography of the broken T2 tensile specimen in the FZ where we find a large number of spherical porosities that is the cause of the 17% decrease in the UTS compared to the BM value.

The inputs for the martensitic microstructure used in the model were produced from SEM micrographs through measurements of the austenite grain size, the martensite packet size, the number of packets in an austenite grain, and the number of martensite laths in a packet.
The martensite packet size and the number of laths in a packet were measured on intermediate and high magnification SEM micrographs, respectively.
The measurement of austenite grain size was made from low magnification SEM micrographs.
The digitized image showed the actual austenite grain size and size distribution.
The austenite grain size and shape remained unchanged above the Ms temperature.

%Si eutectic which was observed at the grain boundaries of the 4047A wire feed welds was closely related with the reduced solidification cracking susceptibility.
Autogenous weld contained transverse cracks at the columnar grain area.
Journal Title and Volume Number (to be inserted by the publisher) 3 did not occur at the weld center region where fine equiaxed grains were developed.
When EPMA was carried out for the segregated constituents at the grain boundaries of the welds made with 4047A wire, 8 to 12wt.
Existence of eutectic at the grain boundaries are apparent for the welds made with 4047A (Al-12wt.

The epitaxial solidification occurs when the columnar grains of weld pool connects with the base metal grains.
So the columnar grain size depends on the grain size of the base metal.
The motivation of grain refinement by pretension arises from: There is inner stress applied on the grain and grain boundary.
When weld seam and HAZ are heated, lattice distortion and dislocation entanglement will increase, which lead to the formation of fine grains through epitaxial solidification of melting weld metal, at the meanwhile the pretension increases the amount of nucleation during the weld joint recrystallization process and reduces the activation energy of recrystallization, which causes the increase of grain number and grain refinement.
The hardness is measured using HVS－5 significant number of small-Vickers hardness, F＝200g，T＝10s.