The preparation and mechanical properties of Al2O3/Ni3Al composites

Al2O3/Ni3Al composites containing 10 vol% of intermetallic phase have been studied in this work. Ni3Al particles with two different morphologies were added to the alumina matrix, viz. Ni3Al as-prepared (AP) by atomization and Ni3Al finely ball-milled (BM) in argon for 96 h. Both AP and BM composites were prepared by pressureless sintering at a relatively low temperature. A s-prepared Ni3Al powder was also mixed with alumina powder, attrition-mille d for 90 min and hot pressed in order to produce a fully dense sample for c omparison purpose. In each case the sintering temperatures (approximate to 1340 degrees C) never exceeded the melting point of Ni3Al, in order not to destroy the favourable ductile microstructure of Ni3Al deriving from the ra pid solidification process. The effect of low sintering temperature resulte d in a density of about 90% for pressureless sintered specimens. The elasti c modulus was 257 and 298 GPa for AP and BM samples, respectively. Fracture toughness and bending strength were observed to increase accordingly for a higher aspect ratio of the intermetallic particles. The hot-pressing proce dure allowed to obtain elastic modulus and bending strength of 372 GPa and 265 MPa, respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.