Recrystallization of an AlMgSi alloy after different modes of hot deformation
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11/7/03
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Recrystallization of an AlMgSi Alloy after Different Modes of Hot Deformation TANJA PETTERSEN and ERIK NES Recrystallization of an AlMgSi alloy has been studied after deformation in torsion and plane strain compression. The main emphasis has been focused on describing the development of nuclei in shear deformed material, and a physically based model has been developed to predict the course of recrystallization in torsion. This model is based on and compared to a previously developed model by Vatne et al.[1–4] describing the recrystallization in plane strain compressed material. To test the model predictions, recrystallization experiments on plane strain compressed and torsionally deformed material have been carried out.
I. INTRODUCTION
THE microstructures of the deformed material, the deformed state, define the conditions for the subsequent recrystallization and annealing processes. Parameters such as the stored energy, the deformation texture, the network of high-angle and low-angle boundaries, and the particle distribution are all important inputs when the objective is to model the recrystallization mechanism.[5] Different deformation modes result in different microstructures and textures, and a model developed for one mode may not be directly transferable to a different mode of deformation. The development of deformation microstructure as well as the recrystallized microstructure and texture in plane strain compressed material has been extensively treated in several previous investigations.[1–4,6–10] The present work does not aim at giving such a thorough investigation, and parts of this presentation will rely on previously obtained results. Deforming a material in plane strain compression is often found to result in a structure consisting of large elongated grains containing a network of cells and subgrains, and constituting a texture typically consisting of the fiber in addition to small amounts of Cube subgrains. When annealing, the Cube texture is found to play a significant role, with the nucleation from Cube subgrains as one of the main nucleation mechanisms.[1–4] Grain boundaries have also been shown to play an important role in nucleation of random grains, in addition to large particles when present. A model containing these nucleation mechanisms has been demonstrated to give a satisfactory description of the recrystallization in a plane strain compressed AlMgMn alloy.[1–4] An important result is that the grain size decreases and the strength of Cube increases with increasing strain prior to annealing. During industrial deformation processes such as rolling and extrusion, the deformation is often seen to be a combination of different deformation modes. The recrystallization process accordingly depends on the preceding deformation process, described by the deformation mode in addition to parameters TANJA PETTERSEN, Senior Engineer, is with R&D Materials Technology, Hydro Aluminium a.s., N-6601 Sunndalsøra, Norway. Contact e-mail: [email protected] E. NES, Professo
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