Mechanical properties and fracture behavior of an Nb-Silicide in situ composite

•We prepared a fine-grained Nb-16Si-10Ti-10Mo-5Hf in composite by mechanical alloying + hot pressing sintering.•Mechanical properties of this composite at ambient temperature and elevated temperature were evaluated in tension.•This composite exhibits notably high tensile strength at elevated temperature.•This composite also shows extensive plasticity or superplasticity at high temperature.

An Nb-Silicide in situ composite with a nominal composition of Nb-16Si-10Ti-10Mo-5Hf (at. %) was fabricated by mechanical alloying followed by hot-pressing sintering. The microstructure consisted of an Nb solid solution, Nb5Si3 and a small amount of Nb3Si. This in-situ composite exhibited good balance of strength between ambient temperature and high temperatures; the ultimate tensile strength was 413 and 496 MPa at room temperature and 1200 °C, respectively. The tensile fracture behavior was dominated by cleavage of the Nbss and Nb5Si3 at 1200 °C and lower temperatures. However, the fracture behavior was governed by ductile rupture of Nbss at 1300 °C and higher temperature, which was ascribed to both the increased ductility of Nbss and the decreased interface strength. At 1400 °C and higher temperature, the material exhibited extensive plasticity or superplasticity; the dominant deformation mechanism was grain boundary sliding at 1400 °C and higher temperature.