Thermomechanical Behaviour of TiB2-AlN Composites

An attempt was made to correlate the compositions and microstructures of AlN-TiB2 particulate composites with their thermomechanical properties. The compaction at 1900C of commercially available powders (AlN and TiB2), under an isostatic argon pressure of 195 MPa, led to the formation of dense composites (relative density of 99%). Various grades of powders were used. The composite obtained by mixing the finest grain powders at a composition of 75 mol% of TiB2 and 25 mol% of AlN, has a Vickers microhardness of 3862 plus or minus 638, strength of 623 plus or minus 60 MPa, and a toughness of 5.6 plus or minus 0.2 MPa.m1/2. When the material was heated to 1000C, creep deformation was not detected. On the other hand, a constant increase in Young's moduli and thermal expansion coefficients was found with increasing TiB2 content. 11 refs.