Superconducting radio frequency (SRF) cavities made from high purity niobium are commonly used in particle accelerators. An understanding of the relationship between mechanical and functional properties and the processing history is essential in order to manufacture cavities with uniform performance. The crystallographic texture and microstructure in polycrystalline sheet varies considerably and identifying its influence on properties is needed to achieve a better understanding of how to control properties of high purity niobium. Texture (preferred crystal orientations) strongly affects mechanical properties and formability of metals and alloys. Samples received from many lots of material from two companies, Tokyo Denkai and Ningxia, for building cavities for the Facility for Rare Isotopes were examined to identify relationships between these two properties. Texture of the undeformed niobium samples through thickness was measured using Orientation Imaging MicroscopyTM system (OIM). Texture was identified with pole figures (PF), orientation distribution function (ODF) and grain misorientation relationships. Stress-strain testing was done to identify ultimate tensile stress (UTS), elongation, 0.2% yield strength, and hardening rate. From tests on many lots, there was no clear trend between the mechanical and material properties in high purity niobium and correlations between various microstructural and mechanical properties showed significant scatter and few apparent correlations.
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