Current modifications of Ti-based materials with porous scaffolds for achieving biological fixation often decrease corrosion fatigue strength () of the resultant implants, thereby shortening their service lifespan. 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 denoted 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 modified Ti-6Al-7Nb was propagation controlled. Moreover, the crack propagation behavior in the PBF scaffold's fusion zone (FZ) and heat-affected zone (HAZ), exhibiting insensitivity to the microstructural configurations characterized by columnar prior-β grain (PBG) boundaries and acicular α′ martensites, coupled with the PBF-induced residual tensile stresses in these regions, resulted in a considerable decrease in for porous scaffolds modified P-Ti6Al7Nb compared to P-Ti6Al7Nb. In contrast, step-wise graded porous scaffold-modified S-Ti6Al7Nb demonstrated an improved 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 resistance of porous scaffolds modified S-Ti6Al7Nb.

中文翻译：

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增材制造梯度多孔支架涂层 Ti-6Al-7Nb 合金的增强腐蚀疲劳强度


目前为实现生物固定而对钛基材料进行多孔支架的改性通常会降低所得植入物的腐蚀疲劳强度，从而缩短其使用寿命。为了解决这个问题，目前，使用激光粉末床在经过最佳表面机械磨损处理（SMATed）的Ti-6Al-7Nb（具体表示为S-Ti6Al7Nb）上增材制造了逐步分级的多孔Ti-6Al-7Nb支架融合（PBF）技术。研究了改性 S-Ti6Al7Nb 多孔支架的显微组织、结合强度、残余应力分布和腐蚀疲劳行为，并与机械抛光 Ti-6Al-7Nb (P-Ti6Al7Nb)、S-Ti6Al7Nb 和改性 P 多孔支架进行了比较。 -Ti6Al7Nb。结果表明，改性Ti-6Al-7Nb多孔支架的腐蚀疲劳是扩展控制的。此外，PBF 支架的熔合区 (FZ) 和热影响区 (HAZ) 中的裂纹扩展行为表现出对以柱状先验 β 晶粒 (PBG) 边界和针状 α′ 马氏体为特征的微观结构配置不敏感，再加上与 P-Ti6Al7Nb 相比，PBF 在这些区域引起的残余拉应力导致改性 P-Ti6Al7Nb 多孔支架的残余拉应力显着降低。相比之下，逐步梯度多孔支架改性的S-Ti6Al7Nb表现出改进，甚至高于P-Ti6Al7Nb。腐蚀疲劳强度的这种进步主要归因于底层 S-Ti6Al7Nb 基体内存在残余压应力，延伸到 FZ 和 HAZ 之外。 这些应力增加了裂纹扩展阈值，导致裂纹偏转/分支并增加了裂纹路径弯曲度，从而协同显着增强了改性 S-Ti6Al7Nb 多孔支架的裂纹扩展阻力。