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MM: Fachverband Metall- und Materialphysik

MM 16: Phase transitions II

MM 16.4: Vortrag

Dienstag, 27. März 2007, 12:30–12:45, H4

Simulation of plate shaped second phase particles — •Emmanuel Jannot¹, Volker Mohles¹, Günter Gottstein¹, and Barend Thijsse² — ¹Institut für Mtellkunde und Metallphysik, RWTH Aachen, Aachen, Germany — ²TU Delft, the Netherlands

In several metallurgical systems, plate shaped precipitates are observed. The most well-known example are the GP zones in AlCu alloys, composed of layers of pure copper in the [1 0 0] plane. This morphology is usually attributed to the conjugate effect of a size mismatch between the solute and the matrix atoms and an elastic anisotropy of the fcc lattice, the <1 0 0> direction being the soft and the <1 1 0> the hard direction. The object of this work is to assess the validity of this assertion. For this purpose a MonteCarlo approach is used where the Metropolis algorithm allows finding stable atomic configurations. The configuration energy is evaluated by Molecular Statics. The input parameters of this study are the potentials describing the atomic interactions. At first, harmonic potentials are employed. Using them, a condition for the stability of the plate morphology is found. This result is confirmed using various kinds of pair potentials (Lennard-Jones*). Moreover the Matrix-Solute interaction can be designed to reproduce the precipitate thermal stability. An interfacial energy of 0.08 J/m2 is derived for GP zones in AlCu alloys. Eventually, the influence of dislocations is studied. Simulation results are compared with TEM observations and a mechanism for heterogeneous precipitation in AlCu alloys is proposed.