Microstructural features and mechanical properties of Al₂O₃-Al₂TiO₅ composite processed by gel assisted ceramic extrusion

Abstract

The influence of aluminium titanate particulates as second phase reinforcement for alumina matrix composites has been investigated with respect to sintering characteristics, microstructural development, and associated mechanical properties. Composites were fabricated by gel assisted extrusion, using boehmite gel as binder. The aluminium titanate precursor was synthesised by a sol-gel technique and dispersed intimately in the alumina matrix by a colloidal method. A boehmite sol was used as dispersing medium and the extrudable composite paste with high viscosity and yield stress was obtained by controlled gelation followed by filtration. The extruded composite was dried and sintered at a temperature in the range 1350-1550°C. The sintered bodies were characterised in terms of density, room temperature flexural strength, microhardness, and microstructure. Aluminium titanate contents up to 10 wt-% were found to lower the sintering temperature of alumina, from 1550 to 1400°C. The composite sintered at 1400°C attained 97% of theoretical density and showed room temperature flexural strength of 318 MPa and microhardness of 21 GPa. The addition of aluminium titanate resulted in a high density alumina composite at lower sintering temperature with an average grain size of about 2 μm.