SKM 2023 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 23: Poster II

MM 23.3: Poster

Dienstag, 28. März 2023, 18:15–20:00, P2/OG1+2

Trapping and detrapping of excess vacancies during natural ageing in Al-Cu — •Tobias Stegmüller, Johannes Berlin, Andreas Schuß, and Ferdinand Haider — University of Augsburg, Chair for Experimental Physics I, Universitätsstr. 1, 86159 Augsburg

A special feature of Al-Cu alloys is the occurrence of decomposition in supersaturated solid solutions by the formation of Guinier-Preston zones (GPZ) even at ambient temperature, where the equilibrium diffusion coefficient is far too low for any unmixing. A condition for this natural ageing is the existence of excess vacancies which remain in the material after quenching from the homogenisation temperature. As the ageing process proceeds for surprisingly long times (hours or days), the vacancies seem to be stabilised in the material and do not decay to the equilibrium value, which would stop the ageing.

Although there exist theories on the stabilisation of excess vacancies, there is no established and verified model to explain the effect. To illuminate the mechanisms behind the long term formation of GPZ we combine results from TEM and DSC measurements as well as Monte Carlo, molecular static and DFT simulations, which reveal that the GPZ themselves may act as temporal vacancy traps. Values for the trapping energy for vacancies in GPZ and on dislocations are estimated from simulations.