| The non-oriented silicon steel is a significant soft magnetic material, and the recrystallization texture optimization is an effective means for improving magnetic property. In current industrial production, texture control has mainly focused on reducing the detrimental ? fiber (<111>//ND), whereas the techniques for enhancing the favorable ? fiber (<001>//RD) have not been developed yet. Strip casting has been attracting more and more attention on its application in silicon steel. The solidification feature of strip casting may produce a special initial texture morphology, which will necessarily result in a different texture evolution during the subsequent deformation and recrystallization. However, there is still a lack of systematic study on texture evolution and control in the strip-cast silicon steel.In the present study, twin-roll cast silicon steel strips were used as starting materials, and thin steel sheets with 0.20mm and 0.35mm thickness were produced by conventional cold rolling and annealing. The evolution in microstructure and texture was investigated by means of X-ray diffraction, electronic backscatter diffraction (EBSD) and crystal plasticity calculation. Firstly, the effects of rolling temperature, rolling reduction and annealing temperature on recrystallization texture evolution is studied; secondly, we studies the formation mechanism of strong cube recrystallization texture after high temperature annealing; thirdly, the formation of cube shear bands and cube deformation bands dependent on matrix orientation is researched; and finally, we delve deeply into the micro-process of cube deformation banding in a {113}<361>grain.Recrystallization textures in twin-roll cast silicon steel sheets are closely related with cold rolling reduction, rolling temperature and annealing temperature. The rolling reduction has a similar effect on ?, Cube, Goss and ? recrystallization texture between rolling at 200? and room temperature. Goss reaches maximum intensity at 60% reduction and is subsequently weakened, while ? Cube, and ? textures are enhanced with increasing rolling reduction. At 90% reduction, ? fiber becomes stronger than ? fiber. Generally, the providing parameters of rolling at 200 ? with 82% reduction and annealing at 1200 ? can enhance the ?, Cube recrystallization texture and weaken the y recrystallization texture.A prominent result in the present study is that strong cube texture was obtained after high temperature annealing, with an accurate cube orientation having the orientation density of seven times random at subsurface layer, and a deviated cube orientation to{001}<410> with the orientation density of five times random at central layer. When primary recrystallization is complete, cube, Goss and y recrystallization textures coexist. After high temperature annealing, cube texture preferentially develops by both grain size and number advantages, while Goss and y textures are extensively reduced. The detailed EBSD analysis shows that cube grains nucleate at shear bands within{111}<110> and{111}<112> deformed grains, and at deformation bands within{001}<210>,{114}<481> and{113}<361> grains. Shear bands contribute more cube nuclei than deformation bands according to the statistics of nuclei number. The orientation relationship between shear band and deformed matrix has been built by CPFEM calculation. And the cube shear band can form in the deformed matrix around{111}<110>.Taylor simulation and EBSD analysis were used to study the formation mechanism of cube deformation bands. The simulation results indicate that initial near-cube orientations rotate to {001}<210>,{114}<481> or{113}<361> orientation. Moreove, the EBSD analysis shows that cube deformation bands form in the interior of{001}<210> deformed grains and grain boundary regions of{114}<481>?{113}<361> grains. It can be therefore deduced that cube deformation bands originate from the retention of initial cube orientation in the grain interior when initial cube orientation rotates to{001}<210>, and also originate near grain boundary due to grain boundary restriction when near-cube orientation rotate to{114}<481>?{113}<361>.In order to further clarify the formation of cube deformation bands, microstructure and orientation evolution was analyzed by channel die compression and EBSD measurement. It is found that Cube and{001}<510> grains are apt to retain its original orientation, whereas the grain subdivision occurs in an initial{114}<481> grain with two rotation to {001}<100> and {114}<110> in addition to the retented original orientation. This suggests that cube deformation band form by the orientation retention in original near-cube grains such as {001}<510>and{114}<481> grains.Finally, the micro-process of deformation banding in a{113}<361> grain was studied by quasi in-situ EBSD analysis. At the very early stage, deformation banding firstly occurs near the grain boundary adjacent to {110}<001> grain. Two kinds of deformation banding morphology were observed in different regions:one kind is lamellar structured with a width of 2?45?m and with the increasing width, the misorientation between the deformation band and the surrounding matrix increases, meanwhile the deformation band orientation gradually rotate to cube; the other kind has the almost invariant orientation and the misorientation with repect to the matrix. When deformation bands develop from the grain boundary to the grain interior, the deformation bands width and the misorientation relative to the surrounding matrix decrease, and the deformation bands orientation becomes farther from cube orientation. Since the orientation fluctuation is below 2° along grain boundary and below 4° from the grain boundary to the grain interior, the orientation fluctuation is not the primary reason for deformation band formation. Deformation banding may occur by the strain concentration which result from a neighboring grain.In the present study, the recrystallization texture in twin-roll cast strips was efficiently controlled by conventional cold rolling and annealing methods. A strong cube recrystallization texture was successfully obtained. These progresses can act as the theoretical and technological foundamentals to manufacture high-grade silicon steel by the twin-roll casting process. Furthermore, the deepened understanding on the formation mechanism of cube nuclei, cube deformation bands and cube shear bands can be widely applied in the texture control of other bcc metallic materials. |
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