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M: Metallphysik

M 8: Phasenumwandlungen I

M 8.1: Vortrag

Montag, 8. März 2004, 14:45–15:00, H4

Precipitates in Al-Li: The existence of a precursor phase — •Stefan Müller¹, Walter Wolf², and Raimund Podloucky³ — ¹Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen — ²Materials Design s.a.r.l., 44.av.F.-A. Bartholdi, 7200 Le Mans, France — ³Universität Wien, Institut fuer Physikalische Chemie, Liechtensteinstr. 22A, A-1090 Wien

Although it is generally believed that the δ′ phase of Al₃Li is directly formed from the fcc-based α solid solution by quenching and aging the sample, X-ray small angle scattering results report the existence of a precursory structure in the early stage of the decomposition. By combining density functional theory calculations with a mixed-space cluster expansion and Monte-Carlo simulations we will show that the existence of such a precursor phase sensitively depends on the chosen Li-concentration. Our calculations allow to predict the ground-state diagram, short-range ordering, the size-shape-temperature relation of the L1₂ precipitates, as well as the coherent phase boundaries for both the precursor phase and the δ′ phase.