Thermomechanical properties of a spark plasma sintered ZrC–SiC composite obtained by a precursor derived ceramic route

The thermomechanical behaviour of a spark plasma sintered ZrC-30wt% SiC composite, made with a ceramic precursor, are characterised and compared with monolithic ZrC. At room temperature, the composite and monolith materials exhibit similar elastic properties. The fine microstructure of the composite leads to an improvement of fracture toughness and flexural strength. During sintering of composite, the overall strain associated to the applied load is preferentially accommodated by the plastic deformation of ZrC and to a more restricted degree by the formation of stacking faults through β→α phase transition operating within SiC. As evidenced in the ZrC monolith, the plastic deformation in the ZrC grains of the composite corresponds to dislocation motion and formation of dislocation walls defining cells. The composites and monolithic material show similar compressive creep strain rates, at temperatures from 1500 to 1600°C and stresses between 60 and 100MPa. As suggested by the identified creep parameters and structural observations, it appears that the main deformation mechanism of the composite is preferentially accommodated by the SiC phase through dislocation motion in the crystal core that is rate-controlled by lattice diffusion of Si.