Fundamental mechanisms and modeling of microstructure evolution during beam and powder bed-based additive manufacturing

基于梁和粉末床的增材制造过程中微观结构演变的基本机制和建模

• 批准号: 327889862
• 负责人: Dr.-Ing. Matthias Markl
• 金额: --
• 依托单位: Lehrstuhl Werkstoffkunde und Technologie der Metalle
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/327889862?language=en
• 关键词: Fundamental; mechanisms; modeling; microstructure; evolution

Beam-based additive manufacturing (AM) of metals in a powder bed not only offers the opportunity to build complex, custom-made components of high-performance materials, but also to adjust the local material properties by proficient processing. The variation of solidification conditions enables the modification of microstructure length scales. Additionally, latest research results indicate, that also the texture of the components is adjustable during manufacturing. Therefore, entirely new perspectives are opened regarding optimization of light weight components, because not only the topology, but also the texture of the material is adjustable to the local loads on the component. In order to comprehend and control the texture evolution, the hydrodynamic non-equilibrium solidification process (grain growth, selection and nucleation) needs to be fundamentally understood. Experimental investigations show that especially the mechanisms of nucleation under the extreme conditions of AM are insufficiently resolved and are not reproduced by classical models.The aim of this proposal is to identify, to fundamentally understand and to physically model the microstructure evolution, especially the nucleation under the special solidification. This model should be implemented in existing software, which is developed at our chair. Modeling and verification are experimentally substantiated basing on additively manufactured samples of IN718. At the end of the project the model should predict the solidification structure, grain structure and texture evolution during beam and powder bed-based AM.The project draws on our software for simulating the consolidation process during beam and powder bed-based AM. The software contains a lattice Boltzmann method to describe the hydro- and thermodynamics during melting and solidification. This method s coupled to a cellular automaton modeling the grain structure evolution during solidification neglecting currently grain nucleation. Our new theoretical ansatz contains besides the temperature gradient and the solidification front velocity for the first time additional information about the texture of the previous layers (orientation, spacing of cells/dendrites, segregation) and the local composition of the melt at the interface to the currently processed layer. It should be investigated, how orientation changes at the solidification front in combination with the present segregations in the rapidly melted material (memory of melt) induce grain nucleation by local undercooling. These findings are mathematically utilized for a grain nucleation model.

粉末床中基于束的金属增材制造 (AM) 不仅提供了构建复杂的、定制的高性能材料组件的机会，而且还可以通过熟练的加工来调整局部材料特性。凝固条件的变化可以改变微观结构的长度尺度。此外，最新的研究结果表明，部件的纹理在制造过程中也是可调的。因此，关于轻量级组件的优化开启了全新的视角，因为不仅拓扑，而且材料的纹理都可以根据组件上的局部负载进行调整。为了理解和控制织构演化，需要从根本上理解流体动力学非平衡凝固过程（晶粒生长、选择和成核）。实验研究表明，特别是增材制造极端条件下的形核机制尚未得到充分解决，并且无法通过经典模型重现。该提案的目的是识别、从根本上理解和物理模拟微观结构演化，特别是特殊凝固下的形核。该模型应该在我们主持开发的现有软件中实现。基于IN718的增材制造样品，建模和验证得到了实验证实。在项目结束时，模型应预测基于梁和粉床的增材制造过程中的凝固结构、晶粒结构和织构演变。该项目利用我们的软件来模拟基于梁和粉床的增材制造过程中的固结过程。该软件包含格子玻尔兹曼方法来描述熔化和凝固过程中的流体力学和热力学。该方法与元胞自动机耦合，模拟凝固过程中的晶粒结构演化，忽略当前的晶粒成核。我们的新理论分析除了温度梯度和凝固前沿速度之外，还首次包含有关先前层的纹理（方向、细胞/枝晶的间距、偏析）以及当前处理层界面处熔体的局部成分的附加信息。应该研究凝固前沿的取向变化如何与快速熔化材料中存在的偏析（熔体记忆）相结合，通过局部过冷诱导晶粒成核。这些发现在数学上用于晶粒成核模型。