Straub Thomas, Fell Jonas, Zabler Simon, Gustmann Tobias, Korn Hannes, Fischer Sarah C L
Fraunhofer Cluster of Excellence Programmable Materials, 79108 Freiburg im Breisgau, Germany.
Fraunhofer Institute for Mechanics of Materials IWM, 79108 Freiburg im Breisgau, Germany.
Materials (Basel). 2023 Jan 10;16(2):676. doi: 10.3390/ma16020676.
This study focuses on the influence of additive manufacturing process strategies on the specimen geometry, porosity, microstructure and mechanical properties as well as their impacts on the design of metamaterials. Filigree additively manufactured NiTi specimens with diameters between 180 and 350 µm and a nominal composition of NiTi (at %) were processed by laser powder bed fusion in a first step. Secondly, they structures were characterized by optical and electron microscopy as well as micro tomography to investigate the interrelations between the process parameters, specimen diameters and microstructure. Each specimen was finally tested in a micro tensile machine to acquire the mechanical performance. The process strategy had, besides the resulting specimen diameter, an impact on the microstructure (grain size) without negatively influencing its quality (porosity). All specimens revealed a superelastic response while the critical martensitic phase transition stress decreased with the applied vector length. As a conclusion, and since the design of programmable metamaterials relies on the accuracy of FEM simulations, precise and resource-efficient testing of filigree and complex structures remains an important part of creating a new type of metamaterials with locally adjusted material behavior.
本研究聚焦于增材制造工艺策略对试样几何形状、孔隙率、微观结构和力学性能的影响，以及它们对超材料设计的影响。第一步，采用激光粉末床熔融工艺加工直径在180至350 µm之间、名义成分为NiTi（原子百分比）的细丝状增材制造NiTi试样。其次，通过光学显微镜、电子显微镜以及微观断层扫描对其结构进行表征，以研究工艺参数、试样直径和微观结构之间的相互关系。最后，在微型拉伸试验机上对每个试样进行测试，以获取力学性能。除了最终的试样直径外，工艺策略还对微观结构（晶粒尺寸）有影响，但不会对其质量（孔隙率）产生负面影响。所有试样均表现出超弹性响应，而临界马氏体相变应力随施加的矢量长度减小。总之，由于可编程超材料的设计依赖于有限元模拟的准确性，对细丝状和复杂结构进行精确且资源高效的测试仍然是创建具有局部可调材料行为的新型超材料的重要组成部分。
