Infiltration of tin bronze into alumina particle beds : influence of alloy chemistry on drainage curves

The wetting of angular alumina particle preforms by Cu-Sn alloys is investigated by means of pressure infiltration experiments conducted at 1150°C, using a system enabling dynamic and precise measurements of the metal volume injected into the preform. Wetting is quantified in terms of drainage curves, which plot the volume fraction of molten metal in the packed powder preform (also called saturation) versus the applied pressure. The shape of the curves confirms earlier findings, namely (i) the initial stage of infiltration is dominated by percolation and obeys a universal scaling relation while the metal shape is fractal and (ii) at higher saturation incremental pore-filling is dictated by local pore geometrical characteristics, saturation curves obeying then the Brooks-Corey correlation. According to sessile drop data in the literature, the Cu-Sn system is characterized by relatively small changes in the contact angle with alloy composition (128 to 122°), while the metal surface tension changes by more than a factor two over the whole composition range. One would therefore expect that the drainage curves be indifferently proportional to the molten metal surface tension or the work of immersion: the present data show that this is indeed verified.