Microstructure and mechanical properties of Nb–Mo–ZrB2 composites prepared by hot-pressing sintering

摘要

Nb–Mo–ZrB2 composites (V(Nb)/V(Mo) = 1) with 15vol% or 30vol% of ZrB2 were fabricated by hot-pressing sintering at 2000℃. The phases, microstructure, and mechanical properties were then investigated. The composites contain Nb-Mo solid solution (denoted as (Nb, Mo)ss hereafter), ZrB, MoB, and NbB phases. Compressive strength test results suggest that the strength of Nb–Mo–ZrB2 composites increases with increasing ZrB2 content; Nb–Mo–30vol%ZrB2 had the highest compressive strength (1905.1 MPa). The improvement in the compressive strength of the Nb–Mo–ZrB2 composites is mainly attributed to the secondary phase strengthening of the stiffer ZrB phase, sol-id-solution strengthening of the (Nb, Mo)ss matrix as well as fine-grain strengthening. The fracture toughness decreases with increasing ZrB2 content. Finally, the fracture modes of the Nb–Mo–ZrB2 composites are also discussed in detail.