Abstract: Current modifications of Ti-based materials with porous scaffolds for achieving biological fixation often decrease corrosion fatigue strength (σcf) of the resultant implants, thereby shortening their service lifes-pan. To resolve this issue, in the present, a step-wise graded porous Ti-6Al-7Nb scaffold was additively manufactured on optimally surface mechanical attrition treated (SMATed) Ti-6Al-7Nb (specifically de-noted as S-Ti6Al7Nb) using laser powder bed fusion (PBF) technology. The microstructure, bond strength, residual stress distribution, and corrosion fatigue behavior of porous scaffolds modified S-Ti6Al7Nb were investigated and compared with those of mechanically polished Ti-6Al-7Nb (P-Ti6Al7Nb), S-Ti6Al7Nb, and porous scaffolds modified P-Ti6Al7Nb. Results showed that corrosion fatigue of porous scaffolds modi-fied Ti-6Al-7Nb was propagation controlled. Moreover, the crack propagation behavior in the PBF scaf-fold's fusion zone (FZ) and heat-affected zone (HAZ), exhibiting insensitivity to the microstructural con-figurations characterized by columnar prior-β grain (PBG) boundaries and acicular α' martensites, cou-pled with the PBF-induced residual tensile stresses in these regions, resulted in a considerable decrease in σcf for porous scaffolds modified P-Ti6Al7Nb compared to P-Ti6Al7Nb. In contrast, step-wise graded porous scaffold-modified S-Ti6Al7Nb demonstrated an improved σcf which was even higher than that of P-Ti6Al7Nb. Such an advancement in corrosion fatigue strength is primarily attributed to the presence of residual compressive stresses within the underlying S-Ti6Al7Nb substrate, extending beyond FZ and HAZ. These stresses increased the crack propagation threshold, leading to crack deflection/branching and increased crack-path tortuosity, thereby synergistically markedly enhancing the crack propagation resis-tance of porous scaffolds modified S-Ti6Al7Nb.

Key words: Ti-6Al-7Nb alloy, Powder bed fusion, Graded porous scaffold, Surface mechanical attrition treatment, Corrosion fatigue