A ductile ceramic eutectic composite with high strength at 1,873 K

摘要

Monolithic ceramics are not widely used as structural materials because of their brittleness. Ceramic matrix composites, in which whiskers or fibres of strong ceramics such as silicon carbide or silicon nitride are embedded in a ceramic matrix, offer improved toughness and strength because the energy of cracks may be dissipated at the whisker/matrix interface. Here we describe a strong ceramic composite with a different kind of microstructure, made by unidirectional solidification of an Al_2O_3/GdAlO_3 eutectic mixture. This composite has a microstructure in which continuous networks of single-crystal Al_2O_3 and single-crystal GdAlO_3 interpenetrate without grain boundaries. Rather than brittle fracture, the material displays plastic deformation at 1,873 K owing to dislocation motion, as in metals. The high strength and resistance to brittle failure of this material at such high temperatures augurs well for applications in mechanical engineering.