Reactive spark plasma sintering and solid solution strengthening of B4C-NbB2 composite ceramics br

the B4C-NbB2 composite ceramics were prepared by reactive spark plasma sintering(SPS) at 2000 celcius/50 MPa using NbC and amorphous B powders as raw materials. The effects of the partial replacement of NbC with 0.1 mole fraction of TiC or ZrC on the phase composition, relative density, microstructure, and mechanical properties of prepared ceramics were investigated. The results show that TiB2, ZrB2 formed during the reactive sintering process can be dissolved with NbB2 to form Nb0.9Ti0.1B2, Nb0.9Zr0.1B2 phases respectively. The formation of these solid solutions greatly improves the densification and mechanical properties of the composite ceramics with refined microstructure. The solution of ZrB2 has a better effect than that of TiB2. The relative density, 3-point bending strength, Vickers hardness and fracture toughness of the prepared B4C-Nb0.9Zr0.1B2 composite ceramics reach 99.5%, 676 MPa, 31.0 GPa and 5.5 MPa & BULL;m(1/2), respectively. The improved mechanical properties are attributed to the relative density enhancement, solid solution strengthening and microstructure refinement caused by the formation of solid solution.