The balance of mechanical and environmental properties of a multielement niobium-niobium silicide-based in situ composite

This article describes room-temperature and high-temperature mechanical properties, as well as oxidation behavior, of a niobium-niobium silicide based in situ composite directionally solidified from a Nb-Ti-Hf-Cr-Al-Si alloy. Room-temperature fracture toughness, high-temperature tensile strength (up to 1200 degrees C), and tensile creep rupture (1100 degrees C) data are described. The composite shows an excellent balance of high- and low-temperature mechanical properties with promising environmental resistance at temperatures above 1000 degrees C. The composite microstructures and phase chemistries are also described. Samples were prepared using directional solidification in order to generate an aligned composite of a Nb-based solid solution with Nb3Si- and Nb5Si3-type silicides. The high-temperature mechanical properties and oxidation behavior are also compared with the most recent Ni-based superalloys. This composite represents an excellent basis for the development of advanced Nb-based intermetallic matrix composites that offer improved properties over Ni-based superalloys at temperatures in excess of 1000 degrees C.