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.