Surface nanocrystallization and mechanical enhancement of pure titanium via ultrasonic severe surface rolling

Cathode rollers are core components of electrolytic copper foil production, and the surface crystalline structure is crucial for controlling the copper foil crystallization. Of note, finer grains enable ultrathin foil fabrication. Conventional spinning and polishing produce cathode rollers with micron-scale grains, which are insufficient for advanced ultrathin foils. In this study, a hybrid process combining spinning with ultrasonic severe surface rolling (USSR) was used for cathode roller fabrication. Applying USSR to spun pure titanium refined the surface grains to the nanoscale while significantly enhancing the mechanical properties. Further, microstructural analyses showed that the USSR creates gradient nanostructures through deformation twinning and dislocation interactions. Mechanical property tests showed that the surface hardness increased by 28 %, yield strength increased by 26.4 %, tensile strength increased by 13.3 %, elongation decreased by only 5.2 %, and surface roughness decreased to 0.2 μm. Strengthening arises from synergistic grain boundary refinement, dislocation hardening, and heterodeformation-induced strengthening. These results confirm that the USSR process produces cathode rollers with ultrafine grains and exceptional strength-ductility synergy, advancing ultrathin copper foil manufacturing.