Improvement of grain refinement, homogeneity and thermal stability of commercially pure titanium by trace scandium alloying

With the increase in size of titanium cathode rolls used in the production of electrolytic copper foils, it has become increasingly difficult to control the grain size and uniformity of titanium material. In this study, the impact of trace Sc addition and synergistic recrystallization preparation technique on the grain size and microstructure uniformity of pure titanium was investigated. The results showed that, based on the (3 + alpha dualphase region hot deformation -> cold deformation+annealing process, trace Sc addition could significantly refine the grain size of pure titanium, with grain size reaching 2.96 mu m. More importantly, it also improved the thermal stability of the annealed recrystallized grains and significantly enhanced the microstructure uniformity along the thickness direction, which is beneficial for controlling the fine and uniform microstructure of large-scale pure titanium cathode rolls in industrial production. As the Sc content increases, the tensile strength initially increases and subsequently decreases, while the elongation decreases. The refinement of the as-cast microstructure is mainly attributed to the solute Sc providing undercooling during the solidification process and the inhibitory effect of Sc2O3 particles on the growth of (3 grains. During the (3 + alpha dual-phase region hot deformation process, Sc2O3 particles can refine the dynamic recrystallization microstructure through particle stimulated nucleation (PSN) effect. During the deformation annealing process, the grain boundary segregation of Sc elements and the pinning effect of precipitated phases can suppress grain growth and enhance the thermal stability of statically recrystallized grains.