Regensburg 2022 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 3: Microstructures and Phase Transformations: Metals & Alloys

MM 3.4: Vortrag

Montag, 5. September 2022, 11:00–11:15, H45

2D precipitate growth in a 3D matrix -- Revealing the kinetics of Guinier--Preston zone formation in Al--Cu from atomic Monte Carlo — •Tobias Stegmüller and Ferdinand Haider — University of Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany

Guinier--Preston zones (GPZ) in Al--Cu, constituting the precipitate phase that was already responsible for the hardness increase in the first age-hardenable Al-alloy about 115 years go, still attract attention first because of their special atomic mono- up to multilayer structure of Cu atoms and second due to their even at room temperature occurring formation, requiring an unexpected fast Cu diffusion.

To understand the origin of the GPZ structure, we performed Monte Carlo (MC) simulations mimicking precipitate growth by applying a Cluster Expansion (CE) for Al--Cu. From this we were able to identify an energy barrier above and below the layers of GPZ that is hardly overcome by migrating Cu. With this barrier we are able to explain the morphology of GPZ from a perspective focussing on the growth kinetics. On the one hand, the barrier guides migrating Cu to the layers' edges, supporting 2D growth. On the other hand, Cu atoms moving towards the layers' faces are stopped by the barrier, leading to nucleation of further Cu layers and explaining the multilayer shape.

To study the origin of the high Cu mobility, we recently included vacancies into simulations by switching from the CE based rigid lattice MC to a MC method allowing lattice relaxations by using a neural network interatomic potential. We present first results from this approach with regard to the interaction of vacancies with GPZ.