Fragmented structure of niobium carbide particles in as-cast modified HP alloys

The structure of niobium carbide particles in as-cast heat resistant modified HP40NbTi alloy have been studied by light and electron microscopy, electron microprobe and X-ray diffraction. The niobium carbide particles in the structure of the HP40NbTi alloys are a multiphase polycrystal clusters with inhomogeneous chemical composition and crystallographic form. The boundaries between the crystals of the carbide particle are large-angle; the disorientation angle between crystals is 30-60°. Polycrystalline character of carbides is, probably, connected with the high thermal stress arising at interphase boundaries in the alloy structure at primary cooling of an ingot. The explanation of the polymorphic character of a niobium carbide cluster requires an independent analysis on the basis of a structural and geometrical crystallography.

177