Spontaneous Infiltration of Aluminum‐Silicon Alloy into Silicon Carbide Preforms in Air

Abstract

Fully infiltrated near‐net‐shape composites of SiC‐Al‐Si have been fabricated by dipping carbon‐containing SiC preforms into a molten Al‐40 wt% Si alloy in an open‐air environment at 1500–1600°C for 10 min. The infiltration process operates in two different modes, the reaction‐controlled and the infiltration‐controlled modes. The reaction‐controlled mode operates in the beginning of infiltration and the reaction product between Al‐Si and C is SiC, whereas the infiltration‐controlled mode operates after a certain infiltration depth has been reached, and the reaction product is dominantly Al4SiC4 elongated grains. Typically a fully infiltrated composite consists of a core (the region with Al4SiC4 elongated grain) and a shell (the region without Al4SiC4 elongated grains), and the two regions are separated by an abrupt boundary. The Al4SiC4 in the core is, however, unstable and changes to SiC when the Si concentration in the core increases above a critical value.