Materials Science and Engineering A 479 (2008) 313–323 Elastic strain and texture evolution during tensile testing of peak-hardened Al–Mg–Si-profiles B. Forbord a,∗ , R.H. Mathiesen a , J. M˚ ardalen a , T. Furu b , H.I. Lange a a SINTEF Materials and Chemistry, 7465 Trondheim, Norway b Hydro Aluminium, R&D Centre, 6600 Sunndalsøra, Norway Received 19 February 2007; received in revised form 19 June 2007; accepted 21 June 2007 Abstract In situ high-energy synchrotron X-ray diffraction was used to investigate the deformation response of extruded Al–Mg–Si-profiles in the T6- temper condition. The profiles recrystallised completely during extrusion and were characterised by three distinct zones with a strongly textured and coarse-grained structure in the bulk region (br), while randomly oriented grains were observed closer to the surface. Despite these differences, through-thickness measurements of elastic strains revealed that work hardening is of the same order in the three zones, most likely due to the presence of particles introduced during the T6 heat treatment. Expansive strain normal to the profile surface was observed and explains the appearance of surface roughening. Finally, the degree of grain rotation was found to decrease, as particles reduce dislocation mobility in the grains. © 2007 Elsevier B.V. All rights reserved. Keywords: Aluminium; Synchrotron radiation; Extrusion; Tensile testing; Surface roughening 1. Introduction Different deformation modes encountered in the bulk and sur- face regions (sr) of extruded profiles often lead to considerable through-thickness microstructural differences. In fully recrys- tallised profiles, the resulting microstructure usually consists of randomly oriented grains in the surface region, whereas a coarser and quite strongly textured microstructure is found in the bulk region (br) [1]. The deformation response of 3.0 mm thick Al–Mg–Si-profiles, displaying such microstructures, have previously been investigated in situ by high-energy synchrotron X-ray diffraction in terms of micro- and mesoscopic geometrical distributions and localized evolutions of elastic strains and grain rotations [2]. Analysis at intermediate length scales revealed strongly inhomogeneous through-profile strains, caused by the presence of the three distinct microstructure regions (sr–br–sr) and the compatibility relations that apply at their interfaces. Vari- ations in elastic strains at characteristic microstructure lengths were also found to be considerable, and the evolution and distribution of certain texture components revealed that grain rotations were a non-negligible part of the deformation response, ∗ Corresponding author. Tel.: +47 98230463; fax: +47 73597040. E-mail address: borge.forbord@sintef.no (B. Forbord). also at intermediate plastic deformations. All these factors are decisive to the appearance of surface roughening [3–8], which limits the use of aluminium alloys within, for instance, auto- motive design due to aggravation of properties like reflectivity, adhesion, weldability and ductility [5,9]. In this work, a similar study has been performed for the same alloy in the T6-temper condition. Once again the main objec- tives have been to (i) study the effect of tensile deformation on the elastic deformation response of surface and bulk regions and (ii) identify possible relationships between the strain and texture distribution, mechanical properties and surface rough- ening. Due to the hardening phases in the T6-temper condition, the deformation response of this variant was expected to differ from the T1-variant, and a third objective has therefore been to (iii) identify these differences. 2. Experiments 2.1. Material and sample preparation The present investigation was performed on a 6082-alloy with chemical composition as given in Table 1. After DC-casting the alloy was homogenised by the following cycle: (i) heating from room temperature to 585 ◦ C within 3 h, (ii) annealing for 2 h at 585 ◦ C and (iii) cooling to room temperature by a rate 0921-5093/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2007.06.065