Early Stages of Recrystallization in Equal-Channel Angular Pressing (ECAP)-Deformed AA3104 Alloy Investigated Using Scan
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INTRODUCTION
THE evolution of dislocation structures and textures during cold deformation and annealing of metals has been investigated extensively over the last decades.[1–3] In the case of aluminum, most studies have been carried out on pure Al or single phase alloys.[4–9] Significantly less research has been done on the effect of second-phase particles on deformation and recrystallization processes. The AA3104, which is one of the most important industrial aluminum alloys used for manufacturing beverage cans, contains such particles. Crystallographic aspects of its deformation by cold rolling and subsequent recrystallization of particle containing Al-alloys, were subject of previous works.[10–17] Much less has been published on processes that occur in structures refined via equal-channel angular pressing (ECAP). It was,
HENRYK PAUL, Professor, is with the Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 30-059 Krakow, Poland, and also with the Mechanical Department, Opole University of Technology, 45-758 Opole, Poland. Contact e-mail: [email protected] ADAM MORAWIEC, Professor, is with the Institute of Metallurgy and Materials Science, Polish Academy of Sciences. THIERRY BAUDIN, Professor, is with the Laboratoire de PhysicoChimie de l’Etat Solide, Universite´ Paris-Sud, ICMMO, CNRS UMR 8182, 91405 Orsay, France. Manuscript submitted October 31, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS A
therefore, interesting to investigate the microstructure and texture changes in the ECAP-deformed AA3104. ECAP is one of the most popular variants of severe plastic deformation used to convert conventional coarse grain bulk materials into ultrafine-grained polycrystals.[7,8,18–27] It involves an extrusion of the sample through a die with two mutually perpendicular channels of equal cross sections. In ECAP, the sample undergoes no change in dimensions, and therefore, it can be reinserted into the die to impose more plastic strain. From a practical point of view, it is important that microstructures obtained via ECAP remain reasonably refined after heating to temperatures of further plastic shaping. This resistance to coarsening is a crucial factor that decides about the applicability of extremely refined structures. However, the understanding of the morphology and crystallography of the recrystallization process is not complete. The important problem concerning annealing of ECAP-deformed samples is to understand the influence of orientations of crystallites present in the deformed state on the recrystallization nucleation and to explain the nature of the transformation of flat grains into nearly equiaxed grains. Deformation and recrystallization textures are usually characterized using scanning electron microscopy (SEM) and electron backscattering diffraction (EBSD). The application of this technique is limited because important details of dislocation structures are lost
(e.g., the distribution of the dislocation boundaries). Such details are clearly visible in bright-field images obtained via t
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