Caractérisation de la texture de recristallisation primaire et de la spécialité des joints de grains de tôles de Fe-3%Si par diffraction des electrons rétrodiffusés

Abstract

The EBSP (electron backscattering pattern) technique has been used to verify and to complete a study by Rouag [Thèse de Doctorat d'Etat (1988), University de Paris Sud, Orsay, France] concerning the influence of crystallographic texture and grain boundaries during abnormal growth of Goss grains in Fe-3%Si sheets, grade Hi-B. 1000 individual orientations have been measured at three levels: at the surface, at a fifth of the thickness from the surface and at the middle of the sheet. This technique allows the calculation of a true orientation distribution function (ODF), which is not possible using X-ray (or neutron) diffraction. Indeed, for X-ray diffraction, only the even part of the ODF can be determined. For the even part of the ODF, the results obtained by EBSPs are in good agreement with those obtained by X-ray diffraction and show the importance of the contribution of the odd part (about 20% of the true ODF). Then the minimal value of the orientation number is determined to assess an ODF statistic. This short study shows that it is useful to determine a minimum of 1000 measurements at each level. From these 3000 measurements, the nature of the grain boundaries is determined showing a good agreement with results obtained in the literature. In particular, it appears that the percentage of coincidence site lattice (CSL) boundaries, which is about 10%, does not depend on the sampling position. Moreover, another short study of the influence of orientation number on the nature of grain boundaries shows that a good representation is obtained if about 750 measurements are taken into account.