Microstructures of Niobium Components Fabricated by Electron Beam Melting

This article presents columnar grain structures characteristic of niobium components fabricated by electron beam melting, using two different size and size distribution spherical powders produced by rapid solidification atomization. The precursor powder microstructures are characterized by equiaxed grains while the columnar grain structure in the electron beam melted (EBM)-fabricated products contain dislocation substructures ranging in density from similar to 10(9) to 10(10)/cm(2) as observed by transmission electron microscopy. X-ray diffraction analysis illustrates the variations in orientations in both the processor powders and the fabricated components. Microindentation hardness values ranged from 0.8 GPa for the precursor powders and 1.1 and 0.92 GPa for the EBM-fabricated, solid components.