In situ diffraction during Selective Laser Melting

与传统制造方法相比，选择性激光熔化(SLM)是一种相对年轻和非常复杂的制造工艺，这就是为什么对该工艺的基本了解仍然不够深入。这导致结果部分缺乏重现性，这阻碍了工业应用于批量生产。在这个过程中，这通过部件中的扭曲和裂缝表现出来，这既可能导致部件缺陷，也可能导致机器缺陷。这一联合研究项目旨在获得更深层次的工艺知识，以便能够最大限度地减少工艺中断和部件质量不足的原因，即变形和裂纹形成，从而提高工艺的重现性。为此，用原位衍射法测量和描述了SLM过程中单层凝固过程中的应力形成、织构发展和相变过程。在自行研制的SLM实验台上，利用高能同步辐射进行了测量。有了关于零件应力形成的知识，就可以具体分析和影响加工误差。使用镍基合金Inconel625(IN625)和工业纯钛1级(Tigri)制成的测试零件，研究不同的几何形状、工艺参数和温度分布对残余应力的影响。这两种材料的特点是用途广泛，同时又表现出不同的结构性能。预期结果和数据有助于澄清这一过程中的基本物理关系，这反过来又将使整个过程最优化，并为随后的建模奠定基础。定量结果也可作为输入变量，用于表示工艺参数与未来模拟中连续应用层的循环加热和冷却所导致的残余应力状态之间的函数关系。

Selective Laser Melting (SLM) is a relatively young and very complex manufacturing process compared to conventional manufacturing methods, which is why the fundamental understanding of the process is still insufficiently developed. This results in a partial lack of reproducibility of the results, which impedes an industrial application for series production. In the process, this manifests itself through distortions and cracks in the components, which can cause both component defects and machine defects. This joint research project aims to acquire a deeper process knowledge in order to be able to minimize the causes of process interruptions and insufficient component quality, i.e. distortion and crack formation, and thus improve the reproducibility of the process. For this purpose, the method of in situ diffraction is used to measure and describe the processes of stress formation, texture development and phase transformations in the SLM process during the solidification of individual layers. The measurements are carried out by means of high-energy synchrotron radiation on a self-developed experimental SLM setup during the production of test parts. With the knowledge gained about the stress formation in the work piece, process errors can be specifically analyzed and influenced. The influence of different geometries, process parameters and temperature profiles on the residual stresses will be investigated using test parts made of the nickel-based alloy Inconel 625 (IN625) and commercially pure titanium grade 1 (TiGrI). These two materials are characterized by their wide range of applications while exhibiting different structural properties at the same time. The expected results and data contribute to the clarification of the basic physical relationships in the process, which in turn will enable optimizing the process as a whole and form the basis for a subsequent modelling. The quantitative results also serve as input variables for the representation of the functional relationships between process parameters and residual stress states as a result of the cyclic heating and cooling during the successive application of layers in future simulations.