Heim, K.; Garcia-Moreno, F.; Rack, A.; Banhart, J.: Role of liquid dynamics on the stabilisation of particle-stabilised Al-films. , 2014

Abstract:
Individual metallic films were pulled from molten aluminium alloys containing different types of stabilising particles (0–20 vol.% of SiC or TiB2). A chamber with a controlled atmosphere (<1–2.1×105 ppm O2) and different molybdenum wire frame structures were used. The objective was to discuss stabilisation of metallic foams based on the same melts [Heim, 2013]. Beside in-dividual flat films, a modification of the wire frame structure allowed us to create artificial metallic Plateau borders and keep them liquid in order to study melt dynamics. Drainage, the velocity of the propagating rupture as well as the behaviour of the ceramic particles inside the melt were analysed in-situ both visually via a high-speed camera system and by means of synchrotron X-ray radiography. The oxide surface on the films was studied ex-situ by energy-filtered TEM and the particle distribution by metallography and SEM to discuss their role in stabilisation. We found that the particles and the immobile oxide skin, whose for-mation depends on the level of oxygen in the surrounding atmosphere and the presence of magnesium, are strongly interrelated. Phenomena such as the healing of thin regions in a film or the fixation of moveable clusters at the immobile gas-liquid interface could be discerned. Interactions of particles and oxygen were also visible during film collapse, where at the oxidised surface fixed particles hinder further film retraction, see Fig. 1. We discuss and compare the results obtained to analogous ones related to both aqueous sys-tems and to metallic foams made from the same alloys by injecting air or Ar into a melt.