Static recrystallization and grain growth of accumulative roll bonded aluminum laminates
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Marr Leibniz-Institut für Festkörper- und Werkstoffforschung (IFW Dresden), Institut für Metallische Werkstoffe, D-01069 Dresden, Germany
Tina Krauter and Heinz Werner Hoeppel Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Materials Science & Engineering, Institute I, Erlangen D-91058, Germany
Werner Skrotzkia) Institut für Festkörper- und Materialphysik, Technische Universität Dresden, Dresden D-01062, Germany (Received 27 April 2017; accepted 5 September 2017)
Aluminum laminates of high and technical purity layers were produced by accumulative roll bonding (ARB) at room temperature. To study the thermal stability, the laminates after 2 to 9 ARB cycles were annealed between 100 and 400 °C for one hour. Changes of the microstructure were analyzed by electron backscatter diffraction. For low ARB cycle numbers (4 or below) and 300 °C annealing temperature, the deformed technical pure layers start to recrystallize while the high-purity coarse recrystallized layers experience intralayer grain growth. For higher ARB cycle numbers (6 and 8) and an annealing temperature of 300 °C or above, the ultra-fine grained layers of technical purity are consumed by the layer overlapping growth of high-purity grains producing a banded grain structure. For 9 ARB cycles and at an annealing temperature of 400 °C, a globular grain structure develops with grain sizes larger than twice the layer thickness. The effect of impurities on recrystallization and grain growth of ARB laminates is discussed with regard to tailoring its microstructure by heat treatment. For further analyses, the results are compared with Potts model simulations finding a rather good qualitative agreement with the experimental data albeit some simplified model assumptions.
I. INTRODUCTION
Accumulative roll bonding (ARB) is a method of severe plastic deformation (SPD), which enables to produce high-strength sheets, i.e., semifinished products of technical relevance.1–3 There exist several possibilities to vary the strength, such as roll bonding sheets of the same or of different kinds of materials up to a certain number of cycles. The strength increase results from an enormous defect production (mainly dislocations and grain boundaries) during SPD, which finally leads to a different steady state microstructure in each material. For multilayered ARB laminates, the limiting grain size in the normal direction (ND) can be the layer thickness if the interfaces act as barriers. It is a great challenge during ARB cycling to keep continuous layers by preventing necking and shear band formation. Recently, perfect laminates of high and Contributing Editor: Lei Lu a) Address all correspondence to this author. e-mail: [email protected] Dedicated to Prof. Dr. Hael Mughrabi on the occasion of his 80th birthday. DOI: 10.1557/jmr.2017.386
technical purity aluminum were successfully produced by Chekhonin et al.4 by ARB up to 10 cycles without any annealing steps. In these ARB sheets, the high-purity layers dynamically recrystallize at room temperature, while the t
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