Microstructure and mechanical properties of Nbss/Nb5Si3 in-situ composites alloyed with Mo and W

The mechanical properties of Nb-ss/Nb5Si3 in-situ composite., alloyed with Mo and W have been studied in relation to the microstructure, The samples were prepared by arc-melting, or floating zone melting method to produce a directional structure. Microstructures were characterized by XRD, EPMA and BEL Room temperature fracture toughness and high temperature strength were examined by three point bending test and compression test, respectively. In Nb-5Mo-xW-16Si and Nb-5Mo-xW-20Si( x = 0 similar to 15 mol%) alloy series, the strength increased and fracture toughness decreased monotonously with increasing content of W. Furthermore, the strength of Nb-15Mo-18Si produced by directional solidification was slightly higher than arc-melted samples, but the fracture toughness was extremely low, It is Suggested that intrinsic toughness of Nb-ss, and thickness of Nb-ss-phase in the microstructures are very important to room temperature fracture toughness.