Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 13: Growth

MM 13.4: Vortrag

Montag, 25. Februar 2008, 15:30–15:45, H 0111

On the role of elastic strains in the precipitation of second phases — •Volker Mohles, Emmanuel Jannot, and Günter Gottstein — Institut für Metallkunde und Metallphysik, RWTH Aachen

The use of Green functions allows the efficient resolution of elasticity problems. However, previous attempts to use this methodology to derive the stored elastic energy in a solid solution haven't been fully successful. For example, the one atom thick plate morphology of GP zones in Al-Cu alloys can't be reproduced using the theory developed by Khachaturyan. The present work provides an explanation for this discrepancy. An improved version of the Microscopic Elasticity theory will be presented. Calculations indicate that this improvement reduces the error generated by the use of Green functions to less than 2% compared to Molecular Statics relaxations. Consequently, the role of elastic strains for the precipitation of second phases can be evaluated more precisely. Simulations for model materials revealed that elastic strains should be first considered as a positive driving force for nucleation. For example, the energy gain offered by the concentration of point defects like solute atoms explains the stability of second phases up to the melting point of aluminum for solute atoms having a 10% lattice mismatch. Using the improved theory, new insight on the factors explaining the precipitate morphology is provided. This work confirms the importance to consider elastic anisotropy.