Effect of SiC additions on microstructure, mechanical properties and thermal shock behaviour of alumina–mullite–zirconia composites

This paper describes the effect of additions of silicon carbide (SiC) particles on density, microstructure, mechanical properties and thermal shock behaviour of slip-cast alumina–mullite–zirconia composites. Alumina, zircon and SiC powders were used to prepare highly concentrated (51 vol.% loading) and stable aqueous suspensions by using Dolapix dispersant (0.5 wt.%). The sintering process was carried out in two stages, first at 1600 °C and then 1500 °C, with 2 and 5 h holding, respectively. Densities and thermal shock properties as well as strength, toughness and hardnessof the prepared composites were evaluated. Two-stage sintering process of alumina–mullite–zirconia–SiC (AMZS) composites led to a remarkable grain size reduction and an increase of density. The maximum value of fracture toughness and minimum value of grain size were obtained by using 20 vol.% silicon carbide. Results showed that the addition of SiC particles (20 vol.%) improved the thermal shock resistance (ΔT = 1000 °C) of alumina–mullite–zirconia composites even after 10 heating cycles.

► The residual strength of composites containing 20 vol.% SiC was changed slightly even after 10 heating cycles.
► After sintering, the smallest grain size and highest toughness were measured for composites containing 20 vol.% SiC.
► The above mentioned results were highlighted by using two-stage sintering.