Materials Science and Engineering A 493 (2008) 48–52 Influence of grain size on orientation changes during plastic deformation S. Scheriau ∗ , R. Pippan Christian Doppler Laboratory for Local Analysis of Deformation and Fracture, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstrasse 12, 8700 Leoben, Austria Received 19 February 2007; received in revised form 4 June 2007; accepted 29 August 2007 Abstract Polycrystalline copper, nickel and iron with grain sizes of 100 m, 10 m, 1 m and about 100 nm were deformed in an in situ deformation stage installed in a scanning electron microscope to study the influence of grain size on orientation changes during plastic deformation. By using the electron back scatter diffraction technique, the microstructural evolution and the crystallographic orientation rotation behaviour taking place during tensile deformation were investigated at three different deformation steps. On the basis of the captured data, domains near grain boundaries show different orientation changes as compared to the inner region of a grain, especially in samples with grains larger than 10 m. At grain sizes smaller than 1 m, this distinctive difference between the near grain boundary region and the interior of grains disappears. In summary, it could be shown that orientation changes in grains larger than 1 m differ significantly from the behaviour in submicrometer and nanocrystalline materials. © 2007 Elsevier B.V. All rights reserved. Keywords: EBSD; Orientation changes; SPD; In situ deformation 1. Introduction Formability as well as mechanical properties of metals and alloys exhibit a strong dependence on grain size and grain struc- ture. Despite the vast number of studies on the effect of grain size on the deformation behaviour and the developed substructure [12,13], the controlling processes are not fully understood. Many different techniques have been applied – e.g. X-ray diffraction (XRD), transmission electron microscopy (TEM) – to analyse changes in crystal textures, variations of dislocation densities or to depict selected elements of the developed substructure at a cer- tain strain [14]. Electron back scatter diffraction (EBSD) offers a new tool to study the local evolution of the substructure and microtexture during the deformation experiments [2,3,7,8,10]. In this analysis microstructural evolutions and crystallo- graphic orientation rotation behaviour taking place during tensile deformation at room temperature were investigated in polycrystalline iron, nickel and copper. Special attention is devoted to possible differences in nano and microcrystalline materials. Tensile test specimens were deformed in an in situ ∗ Corresponding author. E-mail addresses: scheriau@unileoben.ac.at (S. Scheriau), pippan@unileoben.ac.at (R. Pippan). deformation stage installed in a scanning electron microscope that is equipped with an EBSD system. Variations in surface and grain boundary characteristics, such as surface deformation, misorientation, and dislocation distribution, that evolve during the in situ deformation, were examined using both scanning electron microscope (SEM) images and EBSD maps. The orien- tation changes in individual grains were traced at three different deformation steps while the evolution of the sample surface was studied during the whole deformation process. 2. Experimental procedure Measurements on the crystal orientation were carried out with an EBSD-SEM system, a TSL EBSD system interfaced to a LEO 1525. The analysed materials were polycrystalline nickel, iron and copper; the chemical analysis is given in Table 1. At first the initial material was severely deformed in a high- pressure torsion (HPT) process [4,6,11]. The samples with a diameter of 14 mm and a thickness of 2 mm were deformed to 3200%. This huge strain corresponds to a steady state where no further refinement of the crystallites takes place. Such kind of deformation leads to the evolution of an ultrafine and even nano- sized grain structure. However, the resulting small crystallites produced by severe plastic deformation (SPD) contain a huge 0921-5093/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2007.08.092