Regensburg 2019 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 29: Microstructure and Phase Transformations
MM 29.3: Vortrag
Mittwoch, 3. April 2019, 15:30–15:45, H46
Kinetic analysis of the precipitation sequence in dilute Al-Mg-Si alloys based on isothermal in-situ high-precision dilatometry measurements — •Robert Enzinger, Elisabeth Hengge, Wolfgang Sprengel, and Roland Würschum — Institute of Materials Physics, Graz University of Technology, Graz, Austria
The precipitation sequence in a dilute Al-Mg-Si alloy is studied utilizing recent progress in high-precision isothermal dilatometry, which yield access to tiny relative length changes Δ L/L in the range of 10−5 that occur on long time scales exceeding 105 s during isothermal ageing. For each forming phase, Δ L/L-contributions arise from the volume excess due to the precipitates and the contraction of the matrix upon precipitation of solute atoms. In this way, the metastable coherent β″- and the semi-coherent β′-phase as well as the stable incoherent β-phase could unambiguously be detected on an absolute scale [1]. Reaction-rate analyses of the Δ L/L measurements based on the Johnson-Mehl-Avrami-Kolmogorov model yield the kinetic parameters for the formation of the β″-phase and either its transformation to or the formation of the β′-phase. By compiling all these findings, the industrial highly relevant time-temperature-precipitation diagrams become easily accessible, which for these types of alloys were so far hard to ascertain with common experimental techniques.
[1] E. Hengge, R. Enzinger, M. Luckabauer, W. Sprengel, and R. Würschum, Phil. Mag. Lett. (2018), DOI: 10.1080/09500839.2018.1542170