Partitioning-driven heat treatments for the microstructural tailoring of additively manufactured medium manganese steels

用于增材制造中锰钢微观结构定制的分区驱动热处理

• 批准号: 534382755
• 负责人: Dr.-Ing. Jérémy Epp
• 金额: --
• 依托单位: Leibniz-Institut für Werkstofforientierte Technologien IWT
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/534382755?language=en
• 关键词: Partitioning; driven; heat; treatments; microstructural

The 3rd generation of Advanced High Strength Steels (AHSS) offers excelling mechanical properties, contributing to the end of the strength-ductility tradeoff. A notable class of AHSS is composed of Medium Manganese Steels (MMnS), which attain their microstructure via intercritical annealing. This heat treatment relies on partitioning phenomena to adjust the chemical composition of austenite, and tailor its mechanical response under load. Conventionally, these steels are cast, submitted to thermomechanical processing and are finally heat treated to obtain their final properties, but processing can be difficult in particular due to macrosegregation of Mn. Currently, new opportunities rise with the possibilities of Additive Manufacturing (AM), which can be used to manufacture MMnS. This project aims to investigate the potential and the specific mechanisms for tailoring the microstructure of MMnS manufactured by PBF-LB/M. In order to achieve different austenite deformation mechanisms, the local chemical composition will be adjusted by subsequent heat treatments which target the enrichment of austenite by partitioning from the martensitic phase. These heat treatments, here denominated as “partitioning driven heat treatments-PDHT”, are possible over a broad range of temperatures activating interstitial and/or substitutional partitioning leading to varying austenite fraction and stability, as well as further microstructural modifications. The main objective of the project lies on establishing a link between microstructural evolution throughout AM, the subsequent PDHTs, and the resulting mechanical properties. Advanced characterization techniques such as atom probe tomography and transmission electron microscopy will be employed to analyze elemental partitioning and accumulation between martensite, austenite and also at their interfaces. Additionally, in-situ X-ray diffraction experiments will be performed to follow precisely the microstructural changes during PDHTs and subsequent mechanical testing. The targeted results will provide an in-depth understanding about the ongoing mechanisms of microstructure evolution during PDHTs and answers two main questions: I- how can the proposed heat treatments be optimized regarding the time/temperature cycle to achieve tailored chemical compositions without compromising the properties of the martensitic matrix and II- how can the austenite deformation mechanisms be preferentially triggered by specific heat treatment conditions to achieve the desired mechanical properties. The microstructure will be tailored to promote one (TRIP or TWIP), or two different deformation and strengthening mechanisms in combination (TRIP + TWIP), achieving tunable mechanical properties.

第三代先进高强度钢（AHSS）具有优异的机械性能，有助于实现强度-延展性平衡。AHSS的一个显著类别是由中锰钢（MMnS）组成，其通过亚温退火获得其微观结构。这种热处理依赖于分配现象来调整奥氏体的化学组成，并调整其在负载下的机械响应。常规地，这些钢被铸造，经受热机械加工，并且最终被热处理以获得它们的最终性质，但是加工可能特别困难，这是由于Mn的宏观偏析。目前，随着增材制造（AM）的可能性，新的机会出现了，增材制造可用于制造MMnS。本项目旨在研究PBF-LB/M制备MMnS微结构的潜力和具体机制。为了实现不同的奥氏体变形机制，将通过随后的热处理来调节局部化学组成，所述热处理的目标是通过从马氏体相分配来富集奥氏体。这些热处理，在此命名为“配分驱动热处理-PDHT”，在宽的温度范围内是可能的，其激活间隙和/或置换配分，导致不同的奥氏体分数和稳定性，以及进一步的显微结构修改。该项目的主要目标在于建立整个AM，随后的PDHTs和由此产生的机械性能之间的联系微观结构演变。先进的表征技术，如原子探针断层扫描和透射电子显微镜将被用来分析马氏体，奥氏体之间的元素分配和积累，也在他们的界面。此外，将进行原位X射线衍射实验，以精确跟踪PDHT和后续机械测试期间的微观结构变化。目标结果将深入了解PDHT过程中微观结构演变的持续机制，并回答两个主要问题：I-如何在时间/温度循环方面优化所提出的热处理，以实现定制的化学成分，而不损害马氏体基质的性质，以及II-如何通过特定的热处理条件优先触发奥氏体变形机制以获得所需的机械性能。微结构将被定制以促进一种（TRIP或TTRIP）或两种不同的变形和强化机制的组合（TRIP + TTRIP），从而实现可调的机械性能。