Coalescence is the rupture of a film between two adjacent bubbles in any type of liquid foam and has pronounced influence on the development of its macrostructure after solidification, mostly leading to larger pores and a wider size distribution. Foamable AlSi6Cu4 + 0.5 wt % TiH2
precursors made following the powder metallurgical route were foamed in a gas-tight X-ray transparent furnace under 500 kPa (5 bar) pressure with subsequent pressure release. Coalescence was investigated by fast X-ray radioscopy at a frame rate of 1250 Hz and an effective pixel size of 9 µm at the beamline ID-19, European Synchrotron Radiation Facility (ESRF), Grenoble, France. A self-developed program yielded the temporal and spatial detection of coalescence events in the acquired radioscopies. We observed the occurrence of film ruptures in a short temporal and spatial distance and we will refer to these phenomena as “avalanches”.
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