~ Pergamon 0008-4433(95)00011-9 Canadian Metallurgical Quarterh', Voh 34, No. 3, pp. 25%263,1995 Copyrigh~ ~ 1995 CanadianInstitute of Mining and Metallurgy Printedin GreatBritain. All rights reserved 0008 4433/95 $9.50+0.00 THE ROLE OF SPECIAL GRAIN BOUNDARIES DURING THE GRAIN GROWTH IN Fe 3%Si K. T. LEE and J. A. SZPUNAR Department of Metallurgical Engineering, McGill University, 3450 University Street, Montreal, Quebec, Canada, H3A 2A7 ( Receired 2 Auqust 1994: in rerisedJbrm 13 Oclober 1994) Abstract An experimental study of the role of coincidence site lattice (CSL) boundaries in the process of grain growth in grain oriented Fe 3%Si has provided important information about the development of texture. Specimens obtained after decarburization were annealed at temperatures both lower and higher than the temperature of secondary recrystallization. The textures of these specimens were analyzed and the frequency of CSL boundaries from all grains was calculated. In addition, the frequency of CSL boundaries with respect to the {110} <001) grains was calculated for the investigated specimens. By comparing the distribution of CSL boundaries obtained for Goss grains and the distribution of CSL boundaries from all grains, it was possible to predict which CSL boundaries affect the Goss grain growth during secondary recrystallization. Our analysis indicates that Goss grains having a high amount ofi25 CSL boundaries before the secondary recrystallization have a lower number of these boundaries during grain growth. Analysis of other types of grain boundaries indicate that development of the { 110} <001 > texture in silicon steel is not influenced by the total number of CSL boundaries, but rather by the frequency of specific CSL boundaries such as the 525 CSL boundaries. In the investigated specimens, the Goss grains have a size advantage over other grains, which can be considered another important factor in the preferred growth of Goss grains. R~sum~--Une 6tude exp6rimentale du r61e des joints CSL dans le processus de croissance des grains dans du Fe 3%Si nous a apport6 des informations importantes 5. propos du dgveloppement 5. des temp6ratures tout ',i la lois plus basses et plus dlevdes que la temp6rature de recristallation secondaire. Nous avons analys6 la texture de ces specimens et nous avons calcul6 la fr6quencie des joints CSL ~, partir de tousles grains. En plus, nous avons calcul6 la fr6quence des joints CSL par rapport aux grains { 100} <001 >, pour les sp6cimens 6tudi6s. On a pu pr6dire quels joints CSL affectent la croissance des grains de Goss pendant le recristallation secondaire et comparant la distribution des joints CSL obtenus pour les grains de Goss et la distribution des joints CSL de tousles grains. Nos analyses indiquent que les grains de Goss ayant une plus grande quantit6 de joints •5 CSL avant la recristallisation secondaire, ont moins de ces joints pendant la croissances des grains. L'analyse d'autres types de grains montre que le d6veloppement des textures {100} <001 ) darts l'acier au silicium n'est pas influenc6 par le nombre total de joints CSL mais plut6t par la fr~quence specifique des joints CSL comme les joints 25 CSL. Pour les sp6cimens 6tudi6s, les grains de Goss, par leur taille, ont un avantage par rapport aux autres grains, ce qui peut 6tre consid6r6 comme un autre facteur important de croissance pr&6rentielle des grains de Goss. 1. INTRODUCTION Fe-3%Si with a sharp {100} <001) texture has been widely used to build high power transformers. This texture, also called the Goss texture [1], is developed during secondary recrys- tallization. In this process, a few grains having {100} <001) orientation grow very large at the expense of the surrounding grains. In order for secondary recrystallization to occur, the growth of other primary grains must be restrained. For this purpose a variety of precipitates such as manganese sulphide and aluminium nitride have been used [2~4]. Recent studies indicate that the character of grain boundaries influences the Goss texture development during the initial stage of secondary recrystallization and the coincidence site lattice (CSL) bound- aries play a special role [5 7]. These CSL boundaries, especially low-Y boundaries, have low energy: therefore, they are less often occupied by precipitates and are mobile while other gen- eral boundaries are inhibited, Until now it has not been clearly understood what role the CSL boundaries play and why Goss grains grow while other grains do not during the initial stage of secondary recrystallization. This paper reports new experimental data, which provide additional arguments in discussing the role of CSL boundaries. The experiments were carried out on decarburized silicon steel specimens that were annealed at temperatures both below and above the temperature of secondary recrystallization, An etch- pit method [8] was used to identify the orientation of each grain and the grain misorientation of each grain boundary. The frequency of CSL boundaries from all grains and the frequency of CSL boundaries between {100} <001) grains and neigh- bouring grains were obtained. This data was used to analyze the effect of CSL boundaries on Goss texture development. 257