Aluminium carbide formation in interpenetrating graphite/aluminium composites

We have produced interpenetrating graphite/aluminium composites by gas pressure infiltration of aluminium alloys with varying silicon content into porous graphite preforms. Infiltration experiments at 750 °C have shown that a silicon content of up to 18 wt.% can reduce the formation of aluminium carbide but cannot completely deter it. Optical and scanning electron microscopy revealed numerous lath-like interfacial aluminium carbide crystals in the μm regime which, however, did not affect the flexural strength of our composites. Severe aluminium carbide degradation was observed within a few days on composites exposed to ambient conditions. Carbide-free composites were produced by reducing the infiltration temperature to 670 °C for the eutectic alloy.