Neutron diffraction – a tool to optimize processing of niobium tubes

Abstract.

Among other techniques, an accelerator unit can be processed by hydroforming of high-purity niobium tubes. This pre-product undergoes a number of processing steps starting with casting until the final hydroforming which leads to the cavities. Very important for a high-quality hydroforming is the texture homogeneity along the perimeter. An experimental method has been developed to verify the texture homogeneity of tubes in a non-destructive way. Due to the high penetration depth of neutrons, an average texture over the complete tube wall was obtained. Two main results are determined: first, in all tubes a texture variation along the perimeter was found, which we correlate to the coarse-grained microstructure of the ingot; second, annealing of the blank increases the inhomogeneity of the microstructure as well as of the texture along the perimeter.