Hot-Pressed ALON-Based Composite Ceramics and Their Mechanical Properties.

Abstract

Microstructure and mechanical properties of hot-pressed ALON-based composite ceramics were investigated. Microstructure of hot-pressed bodies prepared from a starting mixture of Al2O3, AlN and BN, consisted of γ-ALON phase as a matrix and a homogeneously distributed BN phase. The γ-ALON phase was discontinuous in a composite with BN amount >20vol%. However, addition of 2vol% Y2O3 as sintering aid made the microstructure to maintain a continuous γ-ALON network even for BN addition >20vol%. It is considered that grain growth of the γ-ALON phase was enhanced by the addition of Y2O3. The flexural strength of the hot-pressed bodies decreased with increasing the amount of BN addition up to 20vol%, however, addition of BN >50vol% resulted in an increase of strength up to 80-100MPa. The thermal shock resistance of all samples tested was about 200°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.