On the infiltration mode during fabrication of aluminium composite

Porous Al 6061-2Mg-1Sn-3nylon preforms were nitrided and subsequently infiltrated with Al-Si and Al-Si-Mg alloys at different temperatures. Different infiltration modes were identified and confirmed by numerical simulation. When infiltration happens under conditions close to the eutectic points, it proceeds in the conventional slug flow mode with a well-defined infiltration front. However, as the infiltration conditions depart from the eutectic points, the infiltration mode changes gradually to extreme non-slug flow, where the infiltrant preferentially fills small pores irrespective of their distance from the infiltrant entrance, leading to homogeneous infiltrated structures without any infiltration front. The occurrence of different infiltration modes can be attributed to the competition between thermodynamic and kinetic factors. Extreme non-slug flow occurs under thermodynamically favourable conditions where the preform is well wetted by an infiltrant with sufficient fluidity. In contrast, slug flow occurs under kinetically favourable conditions when the low infiltration temperature at the eutectic points makes mass transport difficult.