Foaming experiments on LM25 alloy reinforced with SiC particulates

Al–Si–Mg/SiCP foams were prepared by melt processing route with TiH2 as the blowing agent. The effects of foaming temperature (640 and 670 °C), SiCP size (12 and 21 μm), and volume % (5–20) on liquid foam expansion and subsequent collapse were studied. Irrespective of the particle size, significant collapse was observed in the liquid foam at 670 °C. At the lower foaming temperature of 640 °C, the liquid foam collapse was low to moderate, with finer and higher (15/20%) contents of SiCp resulting in low collapse and the best overall quality. Preferential segregation of particles to gas/metal interface, postulated by earlier investigators, was not observed in the present case. The presence of SiC within the cell walls induced brittleness, and created irrecoverable damage during the initial phase of compressive deformation. The compressive strength of the foams was lower than theoretical predictions. Minor defects such as porosity, present within the cell walls, might be responsible in lowering of the compressive strength.