Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 12: Nanostructured Materials IV

MM 12.3: Vortrag

Montag, 25. Februar 2008, 17:15–17:30, H 0107

Investigation of Natural Aging on Precipitation in Al-Mg-Si Alloys — •Cynthia S. T. Chang, Ingmar Wieler, Nelia Wanderka, and John Banhart — Hahn-Meitner-Institut Berlin, Berlin, Germany

The purpose of this work is to investigate the effect of room temperature storage on microstructural evolution in Al-Mg-Si alloys. Alloy H, with 0.4wt%Mg and 0.4%Si and Alloy F, with 0.6%Mg and 0.8%Si were cast in the laboratory. The alloys were then rolled and solution heat treated (SHT) at 540oC. After SHT, the samples were water quenched and then separated into two batches. One batch was artificially aged at 180oC immediately after SHT, while the other batch was subjected to natural aging before it was aged artificially. Micro-hardness was measured, and Transmission Electron Microscopy (TEM) and Tomographic Atom Probe (TAP) were used to investigate the microstructures of precipitates at different states. From the hardness measurements, it was found that Alloy F possesses a negative strength response which means that its strength is lower when the sample is naturally aged before artificial aging at 180oC. On the other hand, Alloy H possesses a positive strength response. From the TEM and TAP results, the size, shape and density of precipitates were analysed. The results suggest that the negative and positive responses are related to the density and size of the precipitates after natural aging. This influences the nucleation and growth of precipitates during further aging at 180oC.