Hot-pressed ALON-based composite ceramics and their mechanical properties

Microstructure and mechanical properties of hot-pressed ALON-based composite ceramics were investigated. Microstructure of hot-pressed bodies prepared from a starting mixture of Al sub 2 O sub 3 , AlN and BN, consisted of gamma -ALON phase as a matrix and a homogeneously distributed BN phase. The gamma -ALON phase was discontinuous in a composite with BN amount > 20 vol%. However, addition of 2 vol% Y sub 2 O sub 3 as sintering aid made the microstructure to maintain a continuous gamma -ALON network even for BN addition > 20 vol%. It is considered that grain growth of the gamma -ALON phase was enhanced by the addition of Y sub 3 O sub 3 . The flexural strength of the hot-pressed bodies decreased with increasing the amount of BN addition up to 20 vol%, however, addition of BN > 50 vol% resulted in an increase of strength up to 80-100 MPa. The thermal shock resistance of all samples tested was about 200 deg C. However, strength degradation due to thermal shock decreased with increasing the BN fraction. It was considered that the mechanical properties of hot-pressed ALON-based composite ceramics are significantly affected by the formation of BN phase through the pressurized sintering.