Liquid metal embrittlement by Zn in Mn-containing steels with significant austenite content (T07*)

奥氏体含量较高的含锰钢 (T07*) 中的锌导致液态金属脆化

• 批准号: 436810340
• 金额: --
• 依托单位: Max-Planck-Institut für Eisenforschung GmbH (MPIE)
• 依托单位国家: 德国
• 项目类别: Collaborative Research Centres (Transfer Project)
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/436810340?language=en
• 关键词: Liquid; metal; embrittlement; Zn; Mn

The requirement of lowering vehicles weights and increasing passengers’ safety has motivated the development of advanced high strength steels (AHSS) for the automotive industry. Medium and high-Mn steels constitute an important class in this field. Similar to established steels, the steel grades that are used in body-in-white are commonly Zn coated to protect against corrosion. Welding of Zn actively coated AHSS steel sheets and parts, however, can induce liquid metal embrittlement (LME), which limits corrosion protection and crashworthiness. This is especially true for steels with an ultimate tensile strength exceeding 800 MPa. Therefore, the long-known phenomenon of LME has again come into the focus of steel suppliers in the last two decades. What distinguishes AHSS with an increased Mn content from established steel grades is the significant amount of austenite, through which formability as well as crash performance (absorption of crash impact energy) is enhanced. This could be a central reason why LME is a severe phenomenon for some of these AHSS, but this was not yet unequivocally established. The mission of the present project is, therefore, to systematically investigate the role of austenite for LME in Mn-containing high-strength steels. The project makes use of experimental and computational techniques that have previously been developed within the collaborative research center “Steel – ab initio” as well as insights into medium-Mn steels achieved therein, and transfers them to the interaction of Zn with grain boundaries in these steels. Though LME will be addressed as a multiscale phenomenon, the selection of simulations and experiments will be such that materials-related processes at the atomic scale will be in the focus. To this end, ab initio methods will be used to reveal the interplay between chemistry, structure and decohesion in grain boundaries. On the experimental side, a correlative study of structure and chemistry is performed by combining atom probe tomography with scanning electron microscopy and transmission electron microscopy. All the investigations in austenite will be compared to similar situations in ferrite in order to resolve the special role of this phase for LME. Correspondingly, a variety of steel grades will be provided, processed and characterized by the application partner that contains different amounts of austenite and a tensile strength between 800 and 1400 MPa. The combined approach aims identifying key mechanisms for LME in order to systematically improve resistance of AHSS to this effect.

降低车辆重量和增加密码安全性的要求融合了汽车行业的高级高强度钢（AHSS）的开发。中型和高-MN钢构成该领域的重要类。与已建立的钢相似，在白色物体中使用的钢等级通常被涂有Zn涂层以防止腐蚀。但是，Zn的焊接积极涂层AHSS钢板和零件可以诱导液体金属含量（LME），从而限制了腐蚀保护和撞击。对于超过800 MPa的最终拉伸强度的钢尤其如此。因此，在过去的二十年中，LME的长期已知现象再次成为钢铁供应商的焦点。 AHSS与已建立的钢等级的AHS区分开的是大量的奥氏体，通过该钢铁岩的可调节性和碰撞性能（吸收崩溃冲击能量）可以增强。这可能是LME对其中一些AHS的严重现象的主要原因，但这尚未明确确定。因此，本项目的任务是系统地研究奥氏体在含Mn的高强度钢中的奥斯丁岩的作用。该项目利用了实验和计算技术，这些技术先前是在协作研究中心“从头开始”中开发的，以及在其中实现的中型MN钢的洞察力，并将其转移到Zn与这些钢中晶粒边界的相互作用。尽管LME将作为一种多尺度现象来解决，但模拟和实验的选择将是使原子量表与材料相关的过程的重点。为此，将使用AB的启动方法来揭示晶界化学，结构和脱落之间的相互作用。在实验方面，通过将原子探针断层扫描与扫描电子显微镜和透射电子显微镜相结合，对结构和化学的相关研究进行。为了解决LME的特殊作用，将奥氏体中的所有研究与铁素体中的类似情况进行比较。相应地，将提供，处理，处理和表征各种钢等级，其应用伙伴包含不同量的奥氏体和800至1400 MPa的拉伸强度。合并的方法旨在确定LME的关键机制，以系统地提高AHSS对此效果的阻力。