Additive manufacturing (AM) has enabled the fabrication of extremely complex components such as porous metallic lattices, which have applications in aerospace, automotive, and in particular biomedical devices. The fatigue resistance of these materials is currently an important limitation however, due to manufacturing defects such as semi-fused particles and weld lines. Here Hirtisation$^\circledR$ is used for post-processing of Ti-6Al-4V lattices, reducing the strut surface roughness (Sa) from 12 to 6 $\mu$m, removing all visible semi-fused particles. The evenness of this treatment in lattices with $\rho /\rho_{s}$ up to 18.3% and treatment depth of 6.5 mm was assessed, finding no evidence of reduced effectiveness on internal surfaces. After normalising to quasi-static mechanical properties to account for material losses during hirtisation (34-37% reduction in strut diameter), the fatigue properties show a marked improvement due to the reduction in surface roughness. Normalised high cycle fatigue strength ($\sigma_{f,10^{6}}/\sigma_{y}$) increased from around 0.1 to 0.16-0.21 after hirtisation, an average increase of 80%. For orthopaedic implant devices where matching the stiffness of surrounding bone is crucial, the $\sigma_{f}/E$ ratio is a key metric. After hirtisation the $\sigma_{f}/E$ ratio increased by 90%, enabling design of stiffness matched implant materials with greater fatigue strength. This work demonstrates that hirtisation is an effective method for improving the surface roughness of porous lattice materials, thereby enhancing their fatigue performance.

翻译：增材制造（AM）技术使得制造极度复杂的构件如多孔金属点阵成为可能，此类结构在航空航天、汽车及特别是生物医学器件领域具有应用价值。然而，受半熔融颗粒和焊线等制造缺陷影响，这些材料的抗疲劳性能目前仍存在重要局限。本研究采用Hirtisation$^\circledR$工艺对Ti-6Al-4V点阵进行后处理，将支柱表面粗糙度（Sa）从12 $\mu$m降至6 $\mu$m，并去除所有可见的半熔融颗粒。我们评估了该工艺在$\rho /\rho_{s}$达18.3%、处理深度达6.5 mm的点阵中的均匀性，未发现内部表面处理效果降低的证据。在将疲劳性能归一化至准静态力学性能以消除Hirtisation过程中材料损失（支柱直径减小34-37%）的影响后，由于表面粗糙度的降低，疲劳性能呈现显著改善。归一化高周疲劳强度（$\sigma_{f,10^{6}}/\sigma_{y}$）在Hirtisation处理后从约0.1提升至0.16-0.21，平均提高80%。对于需匹配周围骨骼刚度的骨科植入器件而言，$\sigma_{f}/E$比值是关键指标。Hirtisation处理后$\sigma_{f}/E$比值提高了90%，从而能够设计出具有更高疲劳强度的刚度匹配植入材料。本研究表明，Hirtisation是改善多孔点阵材料表面粗糙度、进而提升其疲劳性能的有效方法。