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.

降低车辆重量和提高乘客安全性的要求推动了先进高强度钢（AHSS）的发展。中、高锰钢是这一领域的重要门类。与现有的钢类似，用于白车身的钢等级通常是镀锌的，以防止腐蚀。然而，镀锌AHSS钢板和零件的焊接会引起液态金属脆化（LME），从而限制了其防腐蚀和耐撞性。对于极限抗拉强度超过800兆帕的钢尤其如此。因此，LME这一久已为人所知的现象在过去二十年中再次成为钢铁供应商关注的焦点。与现有钢种相比，Mn含量增加的AHSS的区别在于大量的奥氏体，通过这种奥氏体，可成形性和碰撞性能（碰撞冲击能量的吸收）得到增强。这可能是LME对某些AHSS来说是一种严重现象的核心原因，但这一点尚未明确确立。因此，本项目的任务是系统地研究奥氏体在含锰高强度钢中的作用。该项目利用了先前在“钢从头开始”合作研究中心开发的实验和计算技术，以及对中锰钢的见解，并将其转移到这些钢中Zn与晶界的相互作用上。虽然LME将作为一个多尺度现象来处理，但模拟和实验的选择将使原子尺度上的材料相关过程成为重点。为此，将使用从头算方法来揭示晶界中化学、结构和脱黏之间的相互作用。在实验方面，将原子探针层析与扫描电镜和透射电镜相结合，进行了结构和化学的相关研究。将奥氏体中的所有研究与铁素体中的类似情况进行比较，以解决该相对LME的特殊作用。相应的，应用合作伙伴将提供各种钢种，加工和表征包含不同数量的奥氏体，抗拉强度在800至1400mpa之间。联合方法旨在确定LME的关键机制，以便系统地提高AHSS对这种效应的抵抗力。