The Balance of Mechanical and Environmental Properties of a Multielement Niobium-Niobium Silicide-Based In Situ Composite

摘要

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℃), and tensile creep rupture (1100℃) data are described. The composite shows an excellent balance of high- and low-temperature mechanical properties with promising environmental resistance at temperatures above 1000℃. 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 Nb_3Si- and Nb_5Si_3-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℃.