Effect of heat treatment on the decomposition of TiC–ZrC solid solutions by spark plasma sintering

TiC–ZrC solid solutions at ZrC composition of 5–90 mol% were consolidated by spark plasma sintering of TiC and ZrC powders. The phase decomposition behavior by heat-treatment at 1273–2273 K was investigated. TiC–ZrC solid solutions with 10–70 mol% ZrC decomposed into TiC- and ZrC-rich phases after heat treatment at 1473–2273 K for 3.6 ks. The decomposition resulted in the formation of nodular structures several tens to hundreds nanometers in length with coherent crystal orientation relationship of the TiC-rich phase {100} // ZrC-rich phase {100}. The Vickers hardness and fracture toughness increased with increasing heat-treatment temperature and reached maximum values of 26 GPa and 3.0 MPa m^1/2, respectively, for 80TiC–20ZrC heat treated at 1873 K.