Effect of Cold Rolling Reduction Rate on Secondary Recrystallized Texture in 3 Pct Si-Fe Steel
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I.
INTRODUCTION
THE secondary recrystallization in 3 pct Si-Fe grainoriented electrical steel has been investigated as the development of Goss ({110}h001i) texture is very important to obtain desirable magnetic properties. The mechanism underlying the development of the Goss texture has been frequently discussed based on its dependency on grain boundary character distribution (GBCD) in primary recrystallized texture.[1–15] One proposed mechanism is based on the assumption that grain boundaries with the misorientation angle between 20 and 45 deg play an important role in the selection of secondary recrystallized textures.[1–4] There are some experimental data demonstrating that these grain boundaries have high energy (HE).[16,17] Hayakawa et al.[1] showed that the frequency of HE boundaries around the Goss component in the primary recrystallized texture is the highest among all orientations. Moreover, Goss texture development during secondary recrystallization could be simulated using the assumption that HE boundary has high mobility during the coarsening of precipitates by means of the Monte Carlo method.[2] This model also explained the generation of the {100}h001i component after secondary recrystallization in the case of cross-rolling.[4] TAKESHI IMAMURA, YUKIHIRO SHINGAKI, and YASUYUKI HAYAKAWA, Senior Researchers, are with the Steel Research Laboratory, JFE Steel Corporation, Kawasakidori 1-chome, Mizushima, Kurashiki, Okayama 712-8511, Japan. Contact e-mail: [email protected] Manuscript submitted February 20, 2012. Article published online November 10, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
Another theory argues that coincidence site lattice (CSL) boundaries are responsible for the growth of a particular orientation during secondary recrystallization.[5–7] CSL boundaries are considered to have high mobility because they are special boundaries with low energy. Some reports[8,9] showed that the frequency of R9 boundaries in Goss grains is higher than those for other components in primary recrystallized textures. However, there is a big difference of their frequencies between the HE boundary and the R9 boundary. The former is 60 to 80 pct and the latter is only 2 to 4 pct around the Goss component after primary recrystallization. During secondary recrystallization of grainoriented electrical steel, Goss grain consumes over 10 millions of the other grains. Therefore, it seems to be inappropriate to assume that the advantage of only 2 to 4 pct frequency of the R9 boundary dominates the secondary recrystallized texture. The above-mentioned studies all deal with 3 pct Si-Fe grain-oriented electrical steels. A study on Nb-containing ferritic stainless steels[10] concluded that the HE model could explain the obtained experimental results and the CSL model could not. Recently, a new model called Solid-State Wetting Model[11,12] has been proposed. According to this model, if the energy sum of two boundaries is lower than that of the third boundary at any triple junction where three grains meet, the thir
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