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These precipitates located at austenite grain boundary or in austenite grains.
Carbides at austenite grain boundary formed a continuous network and carbides in austenite grains were unevenly distributed.
Iron liquid temperature near interface rapidly fallen below solidus lines, a larger number of carbides nucleus were formed.
When neighbouring grains contacted with each other, grains growths were stopped.
Grains would stop growth for a short time because of the present of a large number of nuclei, which resulted in significant refinement of microstructure.

Medium size of the grains (about 30 nm) was obtained after 110 hours of milling.
Mechanical properties and corrosion resistance of the steels depend on their grain size, porosity as well as the size and distribution of the phases formed during their processing.
As can be seen. the number and the medium size of pores in the steel obtained by impulse plasma sintering of nanocrystalline powders are much lower than those formed in the steel obtained by conventional sintering of commercial Höganäs powders.
The steel shows nanocrystalline structure (medium size of the grains is 56 nm for ferritic phase and 74 nm for austenitic one).
Medium size of the grains in the nanocrystalline steel are 74 nm for austenite phase and 56 nm for ferrite one.

However, the higher sintering temperature results in larger the grain size, which causes the reduction of the resistivities of Mg-Mn-Zn ferrites.
Then, the initial permeabilities of samples were computed out according to the measured inductances, toroid sizes and the number of windings.
The grain size of sample sintered at 1100oC (Fig.4a) is small and the ferrite is not fully sintered.
With the increase of sintering temperature, the grain grows and the densities of ferrites increase.
However the higher sintering temperature leads to larger grain size, the larger grains cause the reduction of the resistivity of Mg-Mn-Zn ferrites.

Element Si could increase the number of nuclei, and then diminish crystal particles.
On the other hand, element Si could improve the casting performance of alloy, because it could reduce segregation of alloying element, thin grain boundaries, and reduce the number of dendrites.
The excess silicon segregating in grain boundary was detected by EDS analysis.
The increase of the second phase number in the grain boundary leaded to the serve pitting and promotes the self-corrosion of sacrificial anode.
The electrochemical properties were better when the anode has equable size and regular shape and suited-number second phase [12, 13].

N is the total number of crystal grains in the system. fi is the phase field variables that represent local volume fraction of the austenite and ferrite grains.
(2) (3) Here, n is the number of crystal grains at an arbitral local coordinate.
Di is the diffusion coefficient of carbon atom in the ith grain.
The initial microstructure is composed of 20 austenite grains.
The color contour corresponds to the number of subscript of the phase-field variables.

Result show that the grains size decrease with the increment of dopant amount.
Meanwhile, ZrxNi1-xO with x= 0.10 grain size decrease compared to x=0.01 and also promotes abnormal grain growth.
The abnormal grain growth might be due to ZrO2 phases that segregate at the grain boundaries [7].
The results revealed that a small amount of ZrO2 gives an effect on the grain size.
ACKNOWLEDGMENTS The authors would like to acknowledge the materials and mineral resources engineering, USM and short term grant under project number (No. 814184) REFERENCES [1] J.

The grain size became gradually larger and density of ceramic became obviously higher from 1100℃ to 1300℃, but the rising-trend became slower after 1300℃.
The grain growth is not completely when the sintering temperature is 1100℃.
When the temperature rises to 1200℃, the size of grain further increases and the number of holes gradually minishing.
The outstanding difference is the complete growth of grain, and the holes between the grains are basic closure.
The grain boundary segregation is disappearing and the target is sintered adequately.

There are available a number of phenomena occurring during welding that allow weld metal designers the ability to generate macro- and micro-structural features amenable to implementation of composite theory.
A number of phenomena exist in welding which lend themselves to application for creating composite welds.
Reversing weld travel direction between passes in multi-pass welding will achieve grain refinement and reduce anisotropic tendencies in welds [6].
Lines represent dendrite formation with columnar grains.
Tech. of Welding & Joining, Vol. 8, Number 2, (2003), pp. 95-101

The sizes of ferrite grains and cementite particles were about 0.4 μm and 0.1~0.2 μm, respectively.
The grain size of the ferrite is about 0.4 μm.
Meanwhile, the ferrite grain on the surface of the rod is refined.
The average size of few large and deep dimples is about 8 μm, while a large number of small and shallow dimples distribute uniformly, and the average size is about 1 μm, as seen in Fig. 2(b).
Ponge, in: Ultrafine grained materials Ⅲ.

Also, grains located closer to the stir zone extremity had smaller grain sizes and a higher proportion of high angle boundaries.
Table 1: EBSD grain boundary misorientation statistics, in pct.
While the TEM results revealed that grain structures in the stir zoned produced using 1 s and 4 s dwell times were comparable, the average grain size in 4 s dwell time spot welds was slightly larger.
These larger grain size values may be associated with grain growth during the cooling cycle following the welding operation.
Using EBSD to characterize the stir zone and TMAZ microstructures offers a number of advantages compared to TEM, e.g., the variation of grain size across large areas in spot welded joints can be readily captured, see the TMAZ region in Fig. 2.