Grain refinement and texture regulation mechanism of spin-formed commercially pure titanium cathode for electrolytic copper foil

Abstract

The grain refinement and texture regulation mechanism of spin-formed commercially pure titanium (CP–Ti) cathode during annealing were studied by electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the CP-Ti is seriously deformed after spinning, and the internal strain forms are mainly tension in spinning direction (SD), compression in normal direction (ND), and shear in transverse direction (TD). The dynamic recrystallization occurs during the spinning process, and the recrystallization nucleation mechanism is mainly subgrain nucleation. When spin-formed CP-Ti is annealed at 500 °C, the well-defined substructures generated by fragmentation of primary grains during deformation, as well as the cellular substructures formed by rearrangement of high-density entangled dislocations during annealing can evolve into a large number of fine equiaxed and randomly oriented recrystallized grains. In this case, the subgrain nucleation-dominated recrystallization nucleation mechanism can significantly refine grains. When annealed at 560 °C, a large number of tongue-shaped nuclei with similar orientation to the original grain generated at the grain boundaries, the recrystallization nucleation is inferred to be dominated by grain boundary bulge mechanism. Different recrystallization nucleation mechanisms result in different annealing texture evolution behaviors. When annealed at 500 °C, in the rapid nucleation stage of recrystallization (before 30 min), the texture strength is gradually weakened due to many randomly oriented recrystallized nuclei. With increasing the time from 30 min to 60 min, the recrystallization nucleation and growth reach a dynamic equilibrium, the texture strength tends to be stable. When annealed at 560 °C, a large number of recrystallized grains with similar orientation to the original deformed grains are formed. Oriented nucleation results in a strong texture at the short annealing time (5 min), but the competitive growth of different orientations makes the texture strength gradually decrease with the prolongation of annealing time. In any case, the overall texture strength annealed at 560 °C is higher than that annealed at 500 °C under the same annealing time.

Keywords

• Spin-formed commercially pure titanium cathode
• Microstructure
• Recrystallization nucleation
• Texture