The processing and properties of (Zr, Hf)B2–SiC nanostructured composites

(Zr, Hf)B2–SiC nanostructured composites were fabricated by high energy ball milling and reactive spark plasma sintering (RSPS) of HfB2, ZrSi2, B4C and C. Highly dense composites with homogeneously intermixed ultra-fine (Zr, Hf)B2 and SiC grains (100–300 nm) were obtained after RSPS at 1600 °C for 10 min. The densification was promoted by high energy ball milling and ZrSi2 additive. The additives were almost completely transformed into ZrB2 and SiC during densification. The improvement of flexural strength and fracture toughness (641 MPa and 5.36 MPa m1/2, respectively) was achieved. The relationships between the ultra-fine microstructure and mechanical properties were discussed.