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.