Effects of Strain Rate and Annealing Temperature on the Evolution of Microstructure and Texture in Pure Niobium

The evolution of microstructure and texture was investigated during deformation and recrystallization processes in pure polycrystalline niobium. Optical microstructure, X-ray diffraction, transmission electron microscopy, and electron back-scattered diffraction analyses revealed variant behaviors during deformation and recrystallization; herein, the niobium was compressed under 0.01, 0.1, and 1 s⁻¹ strain rates. As the compressive reduction and strain rate increased, more slips interacted in the deformation process, and the {001} 〈110〉 components became the most important textures in the compressed niobium. For the niobium specimens annealed at 1173 K (900 °C), the (111) [1-10], (111) [0-11], and (010) [1-11] orientations were the main textures. Moreover, the (111) [0-11] and (111) [1-10] orientations became weaker in the annealed niobium as the strain rate increased. The {111} components were the primary textures in the compressed niobium specimen recrystallized at 1323 K (1050 °C). The results showed that the texture intensity decreased and Schmid factors increased in the recrystallized niobium as the strain rate increased. The high Schmid factor also implied that compression under a high strain rate before recrystallization would be optimal for continuous deformation in polycrystalline niobium.