Effect of Texture and Microstructure on Tensile Behaviors in the Polycrystalline Pure Niobium

Pure polycrystalline niobium had different texture and microstructure due to the RCD-60, RCD-84 and CD-84 fabrication processes and recrystallization at 1000 degrees C for 2 h. The tensile behaviors and texture evolutions of the niobium were investigated to reveal the correlation of initial texture/microstructure and tensile properties. The crucial differences of microstructure and orientations after recrystallization would influence tensile properties of the niobium. The differences of tensile behaviors during tension testing correspond to the different microstructure and texture evolution in the niobium. The enhanced < 110 > // RD texture during the tensile deformation indicates that orientations of sub-structures are arranging along the tensile axis in the RCD-60 niobium. The RCD-84 and CD-84 niobium present the other phenomenon, that sub-structures near the fracture occur a significant rotation and the < 110 > // RD texture has been slightly changed after tensile failure. The recrystallized niobium fabricated by the RCD-84 obtains excellent tensile properties with ultimate tensile strength of 364 MPa and elongation of 55%. The strain hardening rate of the CD-84 niobium is the highest during the initial stage of tensile deformation, and becomes lower than that of the RCD-84 niobium after the 16% strain. Furthermore, the analysis of Taylor factors is applied to reveal the difference of hardening rates during tensile deformation due to different fabrication and recrystallization processes of the polycrystalline niobium.