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Investigation of Laser Scribing Technics for Reducing Core Loss of Grain-oriented Silicon Steels Y.
Zhu 3, c 1, 2, 3 College of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China a yuhuang_hust@163.com, bliuyongable@yahoo.com.cn, cglzhu@mail.hust.edu.cn Keywords: Laser processing, Laser scribing, Core loss, Orthogonal test, Grain-oriented silicon steel, Technical parameters Abstract.
Introduction Grain-oriented silicon steels have a large market in the field of soft magnetic materials.
According to the statistics, the waste caused by core loss of the grain-oriented silicon steel reaches 4% of the whole waste of electric energy in advanced industrial countries.
Hence, one domain will become two or more, and the core loss of the grain-oriented silicon steel is reduced [2-4].

Investigation on morphologies of the composites shows that the Al2O3 particles distributed along grain boundaries of LiTaO3, which leads to a fine-grained microstructure in the ALT composite ceramics.
A large number of pores are observed in the composites.
The LiTaO3 is difficult to sinter to high density due to the sintering of LiTaO3 proceeds concurrently with grain growth and produces exaggerated grain growth [8].
The average particle sizes of LiTaO3 original powder was ~3 µm, and any growth of grain size was not observed, which leads to a fine-grained microstructure in the ALT composite ceramics.
Acknowledgements This project was supported by National Nature Science Foundation of China under grant number 50372015.

By using this method, a 2-D microstructure can be modeled considering grain orientations as well as individual anisotropic elastic properties in each grain.
Fig. 1 shows the development of surface roughness with increasing number of loading cycles.
Based on EBSD data the grain boundary of each grain is meshed with boundary elements and specific elastic anisotropic properties are considered in each grain depending on the crystallographic orientation.
The phase map in Fig. 7c shows also the expansion of the martensitic phase in grain 1 (in addition to grain 3).
Due to gradual increase of simulated plastic deformation in shear bands the number and size of generated martensite embryos are growing with increasing number of simulated loading cycles.

Groove pressing (GP) is a severe plastic deformation technique for producing ultra fine grain sized microstructures in metals and alloys.
Before pressing, the copper sheets were annealed at 700 o C for 2 h, which gave an average grain size of 78 µm.
Fig. 4 shows the ultimate tensile strength as a function of number of passes for the grove pressed and groove pressed plus cold rolled specimens.
The microstructure of the starting material exhibited equiaxed grains of about 78 µm (Fig. 5a).
Optical microscopy measurements showed grain sizes of 41 µm were obtained after three passes.

Due to the limited number of slip systems, Mg alloys have poor formability which hinders their widespread application.
The grains in the FS zone are equiaxed and recrystallized (Figure 3a), and the grain size (average 12 µm) is significantly decreased compared to that in the BM.
The grain size in the HAZ is comparable to that in the BM, and no significant grain growth was observed.
The average grain size in the TMAZ is also comparable to that in the BM, but it contains a number of recrystallized grains (as determined from the grain size) similar to that shown in the FS zone, which indicates that the TMAZ has suffered plastic deformation and frictional heating during FS processing.
Conclusions (1) For the AZ31 Mg alloy sheet, after the FS processing, the recrystallized grains in the FS zone were formed; the average grain size is ~ 12 µm, which was significantly refined compared to the grain size (25 µm) of the original material.

The results show that the NLEMC can obtain the fine and uniform equiaxed grains structure, its average-area-circle grain diameter is 28.5μm, and its rheoforming parts, hardness is 129Hv.
The non-dendritization of alloy is mainly due to the increasing number of crystal nuclei in melt and elimination of the conditions under which the dendrites grow up.
With respect to the problem of increasing number of crystal nuclei, Fleming etal[13] reckoned that it is resulting from the secondary dendritic branches which will be broken under the action of electromagnetic field, while other experts[11] reckoned that it is mainly due to the increasing number of free crystal grains moving from crystallizer wall under the action of electromagnetic field.
If applying an electromagnetic field to the quasi-solid alloy at the same time, the temperature filed in melt tends to homogenize, and the over-cooled homogenization of the leading-edge portion of crystal grain growth will lead crystal grains to grow in form of uniaxial crystal, as shown in Fig. 3(c).
If applying an electromagnetic field to the quasi-solid alloy at the same time, the temperature filed in melt tends to homogenize, and the over-cooled homogenization of the leading-edge portion of crystal grain growth will lead crystal grains to grow in form of uniaxial crystal.

No secondary phases were observed at the grain boundaries and triple grain junctions, which guaranteed good optical property of the sintered bodies.
Fig.5 (a) and (b) were the triple grain junction and grain boundaries of the specimen, respectively.
The grains were divided by straight grain boundaries and combined contiguously with each other without mini angle grain boundaries, which were helpful to the transmittance of transparent AlN ceramics.
The grain boundaries and triple grain junctions were clean, no secondary phase was observed.
Yu et al. [16] have pointed out that secondary phase and its distributions in the AlN grains would greatly decrease properties of AlN ceramics by the grain boundary phase layer which disrupted the continuous of AlN grains.

Introduction In polycrystalline materials, propagation of a cleavage crack from grain to grain is a complex process.[1] This is because cleavage occurs on well-defined planes and these planes in neighbouring grains do not usually meet in a line at their common grain boundary.
In addition there is a significant number of deformation twins formed on {10-12} planes ahead of the growing crack.
Hence the stepped cleavage has the effect of limiting the amount of grain boundary fracture that is required as cracks propagate from grain to grain.
This minimises the amount of grain boundary fracture needed to accommodate the mismatch between grains.
Accommodation at a grain boundary in low temperature fracture of Zn as the crack propagates from grain A to grain B is shown in (d).

The microstructure contained grains with an average size of 195 nm and 239 nm, respectively.
In the reported work HE was used to refine the grain size of 6082 aluminium alloy.
From the application and economic points of view it is important to minimize the number of extrusion passes required to achieve the required properties.
The grain sizes were determined using the stereological method and XRD analysis, which enabled the average grain size to be determined by measuring the full width at half maximum of the diffraction peak profile.
The nanometric-size of grains in the alloy's structure was confirmed by XRD analysis although The grain sizes were calculated as 195 nm in the multi-pass sample and 280 nm in the single-pass sample.

In Reuss model[9,10]the stress is assumed to be uniform across the sample for all polycrystalline grains.
In the Voigt model the uniform grain elastic strain is assumed to be equal to the elastic macro-strain value.
The influence of the grain interaction model on the sin2ψ plot is shown in the Fig. 4.
Comparison of stresses calculated for four different grain interaction models for ground Ti and Ni alloy.
This work was financed by the Polish National Centre for Science (NCN) basing on the decision number: DEC-2011/01/B/ST8/07394 and by the Polish Ministry of Science and Higher Education grant: 3264/B/H03/2011/40 and statutory research AGH.