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The natural aging behavior of pure ternary Al‐Mg‐Si alloys is investigated by measuring hardness, electrical resistivity and positron lifetime, as well as carrying out thermal analysis and atom probe microscopy. It is found that several distinct temporal stages of natural aging can be distinguished in which one of these quantities shows a characteristic behavior and that these times coincide for many of these measurements. The rate of change in the measured data is correlated with proposed solute dynamics during natural aging for both aging that takes place prior to artificial aging (natural pre‐aging) and after artificial underaging (natural secondary aging) heat treatments. Controlling factors for solute dynamics are discussed.

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Titanium hydride was used for foaming the aluminium casting alloy AlSi6Cu4. In order to improve foaming characteristics the TiH 2 powder was subjected to various heat treatments prior to processing to shift hydrogen release up into the melting range of the alloy. Untreated and pre-treated powders were characterised by oxygen analysis, thermal analysis in connection with mass spectrometry applying various temperature profiles, X-ray diffraction and transmission electron microscopy. In addition, foaming trials were carried out based on various TiH 2 powders. It was found that oxidation of TiH 2 particles is responsible for the observed shift in decomposition temperature since heating under argon did not produce this effect. The shift can be tailored by choosing suitable pre-treatment parameters. For an appropriate choice a beneficial effect on foam morphology was found.

We present a quantitative study of the catalytic activity of well-defined faceted gold-palladium nanoalloys which are immobilized on cationic spherical polyelectrolyte brushes. The spherical polyelectrolyte brush particles used as carriers for the nanoalloys consist of a solid polystyrene core onto which cationic polyelectrolyte chains of 2-aminoethyl methacrylate are attached. Au/Pd nanoalloy particles with sizes in the range from 1 to 3 nm have been generated which are homogeneously distributed on the surface of the spherical polyelectrolyte brushes. The reduction of 4-nitrophenol has been chosen as a well-controlled model reaction allowing us to determine the catalytic activity of the nanoalloys as a function of the Au/Pd composition. The adsorption behavior was studied by Langmuir-Hinshelwood kinetics. We find a pronounced maximum of the catalytic activity at 75 molar % Au. A comparison of gold, platinum, palladium and gold-palladium alloy nanoparticles is made in terms of Langmuir-Hinshelwood kinetics. Density functional calculations for Au/Pd clusters with up to 38 atoms show that the density of states at the Fermi level increases with increasing Pd content, and that the highest occupied orbitals are associated with Pd atoms. The calculations confirm that small changes in the atomic arrangement can lead to pronounced changes in the particles' electronic properties, indicating that the known importance of surface effects is further enhanced in nanoalloys.

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