%0 Journal Article %T Effect of strain rate on tensile mechanical properties of high-purity niobium single crystals for SRF applications %+ I-Cube Research %+ Institut de Recherche Dupuy de Lôme (IRDL) %+ Michigan State University [East Lansing] %+ Arizona State University [Tempe] (ASU) %+ Imperial College London %+ European Organization for Nuclear Research (CERN) %+ Max-Planck-Institut für Eisenforschung GmbH %A Croteau, Jean-François %A Pai Kulyadi, Eureka %A Kale, Chaitanya %A Siu, Derek %A Kang, Di %A Perez Fontenla, Ana Teresa %A García-Tabarés Valdivieso, Elisa %A Bieler, Thomas R. %A Eisenlohr, Philip %A Solanki, Kiran N. %A Balint, Daniel Stephen %A Hooper, Paul A. %A Atieh, Said %A Jacques, Nicolas %A Cantergiani, Elisa %< avec comité de lecture %@ 0921-5093 %J Materials Science and Engineering: A %I Elsevier %V 797 %P 140258-1 - 140258-15 %8 2020-10 %D 2020 %R 10.1016/j.msea.2020.140258 %K Stress/strain measurements %K Niobium %K Single crystal %K High strain rate %K Anisotropy %K SRF %Z Engineering Sciences [physics]/Materials %Z Engineering Sciences [physics]/Mechanics [physics.med-ph]Journal articles %X An investigation of the mechanical properties of high-purity niobium single crystals is presented. Specimens were cut with different crystallographic orientations from a large grain niobium disk and uniaxial tensile tests were conducted at strain rates between 10-4 and 103 s-1. The logarithmic strain rate sensitivity for crystals oriented close to the center of a tensile axis inverse pole figure (IPF) is ~0.14 for all strain rates. The strain at failure (ranging from 0.4 to 0.9) is very sensitive to crystal orientation and maximal at ~10-2 s-1 for crystals oriented close to the center of an IPF. The high anisotropy observed at quasi-static strain rates decreased with increasing strain rate. The activation of multiple slip systems in the dynamic tests could account for this reduction in anisotropy. A transition from strain hardening to softening in the plastic domain was observed at strain rates greater than approximately 6 × 10-2 s-1 for crystals oriented close to the center of a tensile axis IPF. Shear bands were observed in specimens with orientations having similarly high Schmid factors on both {110}and {112}slip families, and they are correlated with reduced ductility. Crystal rotations at fracture are compared for the different orientations using scanning electron microscopy images and EBSD orientation maps. A rotation toward the terminal stable [101] orientation was measured for the majority of specimens (with tensile axes more than ~17° from the [001] direction) at strain rates between 1.28 × 10-2 and 1000 s-1. %G English %2 https://ensta-bretagne.hal.science/hal-02956353/document %2 https://ensta-bretagne.hal.science/hal-02956353/file/S092150932031323X.pdf %L hal-02956353 %U https://ensta-bretagne.hal.science/hal-02956353 %~ UNIV-BREST %~ ENSTA-BRETAGNE %~ CNRS %~ UNIV-UBS %~ UBS %~ ENIB %~ IRDL %~ ENSTA-BRETAGNE-MECA %~ TEST-HALCNRS %~ ENSTA-BRETAGNE-PTR3-IRDL %~ ELSEVIER