The preparation and mechanical properties of Al 2O 3/Ni 3Al composites

Abstract

Al 2O 3/Ni 3Al composites containing 10 vol% of intermetallic phase have been studied in this work. Ni 3Al particles with two different morphologies were added to the alumina matrix, viz. Ni 3Al as-prepared (AP) by atomization and Ni 3Al finely ball-milled (BM) in argon for 96 h. Both AP and BM composites were prepared by pressureless sintering at a relatively low temperature. As-prepared Ni 3Al powder was also mixed with alumina powder, attrition-milled for 90 min and hot pressed in order to produce a fully dense sample for comparison purpose. In each case the sintering temperatures (≈1340°C) never exceeded the melting point of Ni 3Al, in order not to destroy the favourable ductile microstructure of Ni 3Al deriving from the rapid solidification process. The effect of low sintering temperature resulted in a density of about 90% for pressureless sintered specimens. The elastic 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 procedure allowed to obtain elastic modulus and bending strength of 372 GPa and 265 MPa, respectively.