Preparation and properties of NiAl(Si)/Al2O3 co-continuous composites obtained by reactive metal penetration

Reactive metal penetration was used to prepare intermetallic–ceramic composites with co-continuous structure, starting from silica glass preforms. Two subsequent metal penetrations were performed: first, the silica was immersed in a liquid Al bath, obtaining an Al(Si)/Al2O3 composite, then Ni was put in contact with the composite at high temperature, bringing to the substitution of Al with a Ni–Al intermetallic. The obtained composites present both phases continuous, and the whole process is a near net-shape one. The intermetallic phase is based on the Ni–Al system, with small Si content (lower than 2%) and its composition ranges from Al3Ni2 to a mixture of NiAl and Ni3Al depending on the Ni content during the second penetration step. The composites present high hardness and melting point, low thermal expansion coefficient and good mechanical properties.