Study of the effects of Zr addition on the microstructure and properties of Nb-Ti-Si based ultrahigh temperature alloys

The effects of alloying with Zr on the microstructure, mechanical and oxidation properties of Nb-Ti-Si based ultrahigh temperature alloys have been investigated in this study. The microstructures of the all alloys were comprised of primary γ(Nb,X)5Si3 blocks, Nbss and eutectic colonies, and the additions of Zr do not affect the microstructure and phase constituents of Nb-Ti-Si based alloys. Zr improves both the room-temperature toughness and the high-temperature strength. The alloy with addition of 8 at.% Zr shows the highest fracture toughness of 15.01 Mpa·m1/2. The compressive strengths of the alloys are improved to 278.89-293.08 MPa for the Zr-containing alloys when compare with the Zr-free alloy (194.23 MPa). The oxidation resistance of the alloys was also obviously ameliorated with Zr addition, showing a reduced weight gain with the increase of Zr content.