Densification behaviour and microstructure of spark plasma sintered alumina–mullite nanocomposite

Abstract

Spark plasma sintering (SPS) is a consolidation technique that combines high heating and cooling rates with a uniaxial applied pressure which results in short processing time. SPS is successful in producing ceramics with novel microstructures, which are often reported to be made at temperatures lower than ones used in conventional densification techniques. In this work, the densification and microstructure development sequences of the alumina-15 vol% mullite composite during the SPS and the conventional process were compared. Through SPS technique, the fully dense 0.5 µm grain sized alumina composite (99.5% T.D.) was obtained at 1600°C and its microstructure exhibited nanocrystalline in submicron-sized grains. The nanocrystalline grains were arranged in ground-shaped clusters. Vickers hardness and fracture toughness values for spark plasma sintered composite were calculated as 2098 ± 66 kgf/mm 2 and 3.61 ± 0.06 MPa m 1/2 , respectively.