ZrB2-ceramic toughened by refractory metal Nb prepared by hot-pressing

ZrB2-Nb (ZN) composites were prepared through hot-pressing at a temperature of 1800 degrees C. A contribution of Nb was believed a significant influence on the sinterability, microstructure and mechanical properties of ZN composites. The values of flexural strength of ZN composites rang from 395 to 773 MPa, who are dependent on Nb contents. The highest strength obtained for the ZN composite containing 25 vol.% Nb (773 MPa). A fracture toughness of 7.1 MPa m(1/2) of ZN was revealed, which was much higher than that of monolithic ZrB2. The improvement in fracture toughness strongly depended on an introduction of Nb-ZrB2 matrix. Crack deflection and branching were believed to be the toughening mechanism of ZN. (C) 2010 Elsevier Ltd. All rights reserved.