Additive manufacturing of dense and open-porous specimen made of beta-Titan-Niob and material-specific tailoring of their mechanical properties for individualised implant applications

本课题主要研究了基于三周期极小曲面（TPMS）设计的β-Ti-42 Nb激光粉末床熔合（LPBF）点阵结构的结构-性能关系。数值和实验工作的目的是探索结合仿生设计，生物相容性材料和可定制的制造，为未来的骨植入物的应用。最初的工作集中在工艺参数和设计的介观结构缺陷，如表面粗糙度和形状偏差的依赖。根据CT测量得到的名义-实际偏差参数，建立了预测不同TPMS结构中LPBF固有晶格缺陷发生的回归模型。此外，一个过程的物理建模概念的特征不完善的细观结构的数值重建，它允许断言与缺陷相关的机械影响。实验和数值数据的相关性提供了有价值的见解不同的缺陷类型（粗糙度，形状偏差）的整体结构退化的相对贡献。在有针对性的工艺参数调制的基础上，制造出具有高形状和尺寸保真度的分级TPMS晶格，并且通过纳米压痕测量等手段表征局部机械性能。研究的目的是确定晶格形态和由此产生的属性之间的潜在关系，特别强调在晶格（中心/外围）和异质分级区域的位置的影响。高分辨率的材料数据集成到FE计算通过多材料配方和数值结果进行比较，伴随着在原位DIC变形评估。对仿生TPMS支架的疲劳测试和伴随的SEM/EBSD分析一方面提供了对微观结构形态和纹理的相关性的见解，另一方面提供了对损伤引发和累积的见解。在这里，除了竣工配置，还考虑了通过热处理细化的合金状态。最后，推导了疲劳寿命计算规则。通过增材制造技术、创新材料科学和高效有限元模拟的整体研究方法，该项目为未来使用由生物相容性LPBF处理的Ti-42 Nb合金制成的仿生TPMS晶格作为骨植入物提供了基本前提。

In this project, fundamental studies are performed on structure-property relationships of lattice structures designed based on triply periodic minimal surfaces (TPMS) and processed from β-Ti-42Nb by laser powder bed fusion (LPBF). The numerical and experimental work aims to explore the combination of biomimetic design, biocompatible material and customizable fabrication for future bone implant applications. Initial work is focusing on the dependence of mesostructural imperfections such as surface roughness and shape deviation on process parameters and design. A regression model for predicting the occurrence of LPBF inherent lattice defects in different TPMS structures is derived from the nominal-actual deviation parameters determined by CT measurements. Furthermore, a process-physical modeling concept for the numerical reconstruction of the characteristic imperfect mesostructure is developed, which permits assertions about the mechanical implications associated with imperfections. The correlation of experimental and numerical data provides valuable insights into the relative contributions of the different defect types (roughness, shape deviation) to the overall structural degradation. On the basis of targeted process parameter modulation, graded TPMS lattices are manufactured with high shape and dimensional fidelity and the local mechanical properties are characterized by means of nanoindentation measurements, among other things. The studies aim to identify potential relationships between lattice morphology and the resulting properties, with particular emphasis on the influence of location in the lattice (center/periphery) and heterogeneous grading regions. The high-resolution material data are integrated into FE calculations through multi-material formulations and the numerical results are compared with the accompanying in situ DIC deformation evaluations. Fatigue tests on biomimetic TPMS scaffolds and concomitant SEM/EBSD analyses provide insights into the correlation of microstructural morphology and texture on the one hand and damage initiation and accumulation on the other hand. Here, in addition to the as-built configuration, alloy states refined by heat treatment are also considered. Finally, fatigue life calculation rules are deduced. Through the holistic research approach consisting of additive manufacturing technology, innovative materials science and efficient FE simulation, this project provides the basic prerequisite for the future use of biomimetic TPMS lattices made of the biocompatible LPBF-processed Ti-42Nb alloy as bone implants.