SHEAR BANDING IN TWINNED STRUCTURES AND THEIR INFLUENCE ON BRASS-TYPE TEXTURE H. Paul 1 , A. Morawiec 1 , E. Bouzy 2 , J.J. Fundenberger 2 and A. Piątkowski 1 1 Institute of Metallurgy and Materials Science, Polish Academy of Sciences, Kraków, Poland 2 Laboratoire d'Etude des Textures et Applications aux Matériaux, CNRS, Metz, France Keywords: Texture; Shear bands; Transmission electron microscopy; Orientation imaging maps. Abstract. The local crystallography within shear bands (SB) has been examined in a single crystal of {112}<111> orientation of pure copper deformed at 77K by channel-die compression to strains of about 1. Setting up a system for making high-resolution orientation maps using transmission electron microscopy (TEM) has opened new advantageous circumstances for the analysis of orientation changes within SB. This method with spatial resolution higher than 10nm allows the examination of microstructure images composed of nanoscale subcells forming SB. It has been found that for well-developed shear bands, a crystal lattice rotation about <112> direction tends to dominate and this process is usually accompanied by activation of new slip systems. The present work shows that despite the plane strain deformation mode, the mechanism of lattice rotation within emerging SBs may lead to Goss and Brass texture components. Introduction Mechanical twinning in cold deformed low stacking fault energy (SFE) metals is the main microstructural mechanism of large orientation changes. It controls the classical texture transition from the copper-type to the brass-type [1]. Current understanding of the formation of the brass-type texture in rolled low SFE alloys additionally assumes an inhomogeneous deformation, usually in the form of SBs [2]. The so-called brass-type SBs are formed in medium to low SFE metals, in which deformation twinning occurs extensively even at relatively low deformations [3-6]. The main goal of the present work is to understand the texture evolution within deformed low stacking fault energy (SFE) metals, paying particular attention to the occurrence of the specific texture components of SB in copper single crystal deformed at 77K. The experimental conditions were designed to facilitate the occurrence of the microstructure saturated by compact clusters of SB, called macroscopic shear bands (MSB). In earlier publications [6-8] it was shown that the strong textural changes during low temperature channel-die compression of an initially C{112}<111>-oriented copper single crystal are related to dislocation slip, mechanical twinning and shear banding. However, despite considerable interest in shear banding, the elementary mechanisms of SB nucleation, their development within twinned microstructures and, in particular, their contribution to the formation of the brass-type rolling texture are still a matter of debate. Besides the issues listed above, there are other aspects of shear banding on which there is no agreement. The macroscopically observed shear occurs in a plane different than {111} in the matrix and twin lamellae. This leads to the fundamental question whether the mechanisms responsible for SB have a crystallographic character. Moreover, there is the problem of the nature of the (T- M)/(SB) boundary zone; it is not clear how the twin-matrix (T-M) layers are incorporated into a band. Because the shear banding is closely related to textures [6-8], local orientation measurements, and in particular, the orientation maps, constitute a suitable mean of investigating the phenomenon.