Interfacial reactions and wetting in Al-Mg/oxide ceramic interpenetrating composites made by a pressureless infiltration technique

The present paper considers the microstructures of Al-Mg/oxide ceramic interpenetrating composites made by a pressureless infiltration technique. The composites were produced using an Al-10 wt.% Mg alloy with two oxide ceramic foams, spinel (MgAl2O4) and mullite (Al6Si2O13), at 915 °C in a flowing N2 atmosphere. Full infiltration of the aluminium alloy into the ceramic preform has been achieved with good bonding between the metal and ceramic phases. The composites were characterised by a range of techniques and compared with those for alumina from the literature. It has been found that the metal-ceramic interface of the composite consisted of an oxide layer near the ceramic phase and a nitride layer from Mg3N2 to AlN near the metal phase. The improvement of Al wetting and adhesion on the oxide ceramics by the addition of Mg and in the presence of N2 was studied by a sessile drop technique to clarify which compound that formed at the interface contributed to the spontaneous infiltration.