Directionally solidified in-situ composites based on niobium and niobium silicides, such as Nb5Si3 and Nb3Si, are presently under investigation as structural materials [1, 2], Alloying additions of elements such as Hf, Ti and Mo to these silicides are also being explored in order to increase strength and oxidation resistance. The present paper describes the effect of Hf, Mo and Ti additions on microstructure and microtexture of high temperature silcide-based in-situ composites.

Alloys were prepared from high purity elements (>99.9%) using induction levitation melting in a segmented water-cooled copper crucible. The alloys were directionally solidified using the Czochralski method [2], Phase identification was performed using scanning electron microscopy, electron microprobe analysis (EMPA), and automated electron back scattering pattern (EBSP) analysis. Using EBSP, positive phase identification was accomplished by direct comparison of the location and character of the diffraction bands in the experimental pattern with those calculated from simulated patterns generated using the possible structure types.