Papers by Keyword: Strain Induced Boundary Migration (SIBM)

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Authors: Yoshiaki Natori, Kenichi Murakami, Satoshi Arai, Yousuke Kurosaki, Hisashi Mogi, Hotaka Homma
Abstract: Examination of the SIBM mechanism based on the dislocation substructure at the interior of the Goss oriented grain was carried out by changing the grain size prior to the temper rolling. The following results were obtained. 1) SIBM significantly increased Goss orientation during the eminent grain growth with the initial grain sizes from 18 to 55μm. 2) When the initial grain sizes were large, i.e. 37μm and 55μm, the rolling with the reduction beneath the critical value could not promote SIBM, even the normal grain growth could also be hindered. Consequently a proposal was made that the nucleation of the recovery appeared among substructure domains containing sluggish strain. There exists an adequate size of the domain which varies with the change both of the rolling reduction and the initial grain size.
Authors: Jong Tae Park, Kyu Seok Han
Abstract: Semi-processed nonoriented electrical steels are very attractive products whose magnetic properties are significantly improved through annealing treatment in customers plant. The improvement is due to strong Goss texture formation by strain induced boundary migration (SIBM). In order to the effect of temper rolling reduction on the strengthening of Goss texture, temper rolling reduction was changed in the range of 2% to 8%. The annealing times was changed from 10 minutes to 180 minutes. A mechanism of grain growth during SIBM is suggested from our experimental data. In the specimen temper-rolled by 2%, relatively strong {111}<112> texture develops, whereas in the specimens temper-rolled by 4% through 8%, strong Goss texture develops as a result of SIBM during final annealing. It can be found from observed EBSD data that the Goss grains have the lowest stored energy in all temper-rolled specimens, which is confirmed by average image quality value in EBSD measurements. However, for the Goss grains to grow preferentially, stored energy difference between Goss grains and their neighboring grains may have to be higher than a certain critical value.
Authors: Jai Gautam, Roumen H. Petrov, Elke Leunis, Leo Kestens
Abstract: The present paper investigates the potential application of Strain Induced Boundary Migration mechanism on the two different types of surface textures developed after α-γ-α phase transformation annealing, one with preferred cube and Goss orientation at the surface and the other with random surface texture without preferred orientations. It has been demonstrated that these surface texture components grow in across the thickness of the sheet after an appropriate combinations of a critical amount of rolling reductions and an annealing treatment at the recrystallisation temperature.
Authors: Kenichi Murakami, Jacek Tarasiuk, H. Réglé, Brigitte Bacroix
Abstract: Texture formation through strain induced boundary migration (SIBM) was investigated. Temper rolling reduction before final annealing for SIBM was varied between 0 and 26% and grain sizes and textures were measured using EBSD. In the specimen which was temper rolled to 5%, in which grain growth by SIBM occurred most efficiently, a strong Goss component (which was a minor component after rolling), developed during annealing. From the EBSD image quality analysis, it was found that stored energy increased significantly in the Goss component with strain (from 5 to 9 %), whereas it was always relatively small in the D-Cube component ({001}<110>), compared to Goss and g-fibre components. Based on these results, a mechanism of grain growth by SIBM was suggested. Texture evolution during annealing could thus be explained by the hypothesis, speculated from the analysis of orientation stability, that D-Cube grains are associated with more homogeneous dislocations distributions than Goss grains, in which the co-existence of high and low dislocation density zones could favour grain growth by SIBM.
Authors: Kenichi Murakami, T. Kubota, Fabienne Grégori, Brigitte Bacroix
Abstract: In order to elucidate the predominance of Goss grains after SIBM in electrical steel sheets, Goss, D-Cube and {111}<112> grains after temper rolling of 5 and 9% reduction were observed by TEM. In 5% strain the amount of dislocations in Goss grains was the smallest of the three orientations. In 9% strain dislocations in Goss grains were distributed more heterogeneously than the other two types of grains. It is considered that {111}<112> grains have large amounts of dislocations owing to high Taylor factors and the differences of microstructures between Goss and D-Cube grains are due to orientation stabilities. Goss grains are speculated to be easy to recover and therefore they are predominant after SIBM.
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