Effect of carbon on the microstructure and carbides in U-Nb alloy

Influence of carbon on the feature of Nb₂C inclusion and microstructure of an U-5.5Nb alloy were investigated focusing on the detailed metallographic characterization of inclusion concerning their morphology, composition and size distribution and formation mechanism. The methods used in present study are scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) and optical microscopy (OM). The results show that the average grain size of the as-cast U-5. 5Nb alloy decrease significantly with the increase of carbon content due to the heterogeneous nucleation of Nb₂C phase, which can effectively refine the grain size during solidification. Meanwhile, carbon content obviously effects morphology, size distribution, area fraction and number density of Nb₂C inclusions. In addition, the result shows that the Nb₂C inclusion forms in liquid, subsequently, Nb₂C inclusion grows, collides and agglomerates to form clusters. (authors)