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Six test plates with different HIs were welded respectively according to AWS A5.20/ A5.20M: 2005 standard by welding power of Lincoln powerplus-505 and numbered from 1# to 6#.Multi-layer and multi-pass welding process was adopted.
In addition, the metallographic microstructures of coarse-grain zone and fine-grain zone from 1# to 6# are shown in Fig. 4.
In addition, there are a large number of regular-shape inclusions at the bottom of dimples, and this kind of destruction form is peculiar to high toughness materials.
This means that the optimization function of fine-grained region proportion increase to toughness is less than the harm of grain coarsening and grain boundary reduces to that.
It can be seen from Fig. 4 that microstructure mainly contains polygonal ferrite (PF) and acicular ferrite (AF) with a small number of granular bainite (GB).

Grain growth and coalescence was prevalent in the early deformation stage, while grain boundaries were impaired and replaced by dislocation interactions when 24%.
Furthermore, the plastic deformation mechanism would change from dislocation activities to grain boundary sliding and/or diffusion when the grain size is decreased below a certain length scale [2].
For undeformed samples (Fig. 3(a)), the grains are equiaxed and separated mainly by high-angle grain boundaries.
Counting about 400 grains from a number of TEM images, an average grain size of 90 nm with a lognormal distribution from 30 to 200 nm can be obtained.
At 24% (Fig. 3(c)), significant changes occurred in both grain size and morphology.

However, most of the material surface of laser melting treatment is still integrity, but yet severe shedding only occurs in partial grain boundary.
So that grain refinement improves the fatigue strength of 17-4PH steel surface and prevents plastic fracture along the lateral propagation.
Due to stress concentration of the grain boundary, which has been suffered repeated impact, so it is easy for crack formation to be occurred at the grain boundary, leading to plastic deformation.
It is due to using laser treatment make the modified layer rapidly solidify to obtain ultra-fine grain microstructure and improve the surface strength.
Due to the lager number of defects in pits, the formation of new cracks and the superposition of new and original cracks are apt to happen.

Introduction In order to measure edges of diamond abrasive grain, a robust measurement method for vertex position of a small polyhedron using image processing is proposed.
The dp is not getting smaller when the data number is larger.
K is the data number for the in-focus calculation of regression.
An abrasive grain of diamond, measurement target of our research, has shape of a polyhedron.
Selected diamond grains for precise grinding have even shapes of polyhedron.

The structure of the superconducting Nb3Sn layer depends on a number of various factors, such as diffusion annealing temperatures and duration, composite geometry (the number, shape and composition of Nb filaments and Sn sources), doping, etc.
There are areas of various morphology, i.e. with relatively fine grains and small grain size scattering (Fig. 4a), with coarser grains (Fig 4b) and with anomalously coarse grains (Fig 4c).
An average grain size in this specimen is about 106 nm.
It is interesting to note that these particles are mainly located in coarser grains, thus, they do not retard the grain growth, but on the contrary cause grain coarsening.
Diffusion layers mainly possess fine-grained and uniform structure, though there are areas with coarser grains and wider grain size scattering as well as anomalously coarse grains, especially in the wire diameter of 0.7 mm.

In order to determine the number, size and distribution of pores, two rheocasting alloys were investigated using computed tomography (CT).
Number, size and distribution of pores were thus determined using the software package Volume Graphics Studio Max 3.3.
S11)), indicating that a significant grain growth occurs during T6.
The number density is only 0.024 mm-3.
The number density is 0.7 mm-3.

Under the vibration and shear of sloping plate, a relatively homogenous temperature field and composition filed are formed around some grains and are favorable for the direct growths of globular grains; meantime, dendrites formed under the vibration and shear are broken up and rounded gradually and better semisolid slurry is formed.
Large numbers of nucleus escaped the surface of sloping plate and entered into the interior of the melt and were favorable for the nucleus growth of globular crystal.
It can be seen from Fig.2 that the microstructure in position 1 of sloping plate mainly consists of dendrites and fine globular grains; the microstructure in position 2 mainly consists of rosette and globular grains; the microstructure in position 3 mainly consists of globular grains and near-globular grains.
Under the vibration and shear of sloping plate, nucleus escape ceaselessly the surface of sloping plate, and enter the interior of the melt, which is favorable for the formation of large numbers of nucleus inside the melt.
Under the shear and vibration of sloping plate, escaped grains not only move but also rotate [14].

It was found that the grain refinement layer was formed in the thickness of about 100μm .The dislocation density of LY12 aluminum alloy should be large increased after laser shocking because the accumulation of dislocation was appeared on the grain boundary.
With the laser energy density increased there formed subgrain structure and eventually generate ultra-fine grain.
(b) indicates that a large number of distinct accumulation of dislocation appeared in LY12 aluminum alloy.
Figure 2 shows grain refinement after laser impact observed from facula center.
From the photo it can be found that compared to matrix grain, a deeper hardening layer of about 100µm thick was produced on auminum alloy after laser impact, and corrosion-resisting property was greatly improved; this process may be caused by surface grain refinement, however, as for limited experimental conditions, refined grain boundary was not observed, which is to be studied and proved in future.

Estimation Model Since MnZn soft ferrite is a kind of polycrystalline material composed of a great number of grains, the eddy-current losses of single grains in the micro-structure of this material are calculated, and then the eddy-current loss per unit volume of the core is deduced.
Generally, the grains of MnZn ferrite are polyhedrons, but the simplified model in this paper simplifies the grains as spheres.
If the mean radius of the grain (sphere) is, then the time-varying eddy-current loss of a grain, can be found by , (5) in which the grains per unit volume, excluding the grain boundary, is [12].
In this figure, , and represent grain resistance, grain-boundary resistance and grain-boundary capacitance, respectively.
Grain-boundary resistance dominates the impedance of the sample at low frequencies, while grain resistance dominates at high frequencies.

Large grain on the film surface hardly is found.
At low temperature, nucleation free energy declines and the number of the core increases.
This is helpful for grain to grow up.
On the other hand, it is considered that residual stress develops when newly deposited grains are attracted to one another during deposition, causing grain coalescence or “zipping” of the grain boundaries.
Thus, a number of microstructure variables are expected to influence the magnitude of residual stress generated by the grain size and coalescence mechanism.