Mitigating grain-boundary decohesion during liquid-metal embrittlement in advanced high-strength steels

现代高强度钢是基础设施和汽车行业的关键材料。第三代高强度钢的持续发展伴随着一个几十年的问题：一旦镀锌（镀锌）来钝化钢，如果结合融化锌的方法，可能会出现显著的性能恶化。实际上，液态金属与固体基体（这里是锌和钢）接触时共存，通过晶界现象导致脆化，称为液态金属脆化（LME）。作为工业面临的一个紧迫问题，需要有基本的方法来理解和减轻现代钢材的LME。基于我们早期的工作发现，在LME微裂之前，纳米级晶界削弱了金属间相的形成，并确定了偏析转变是其原因，我们开始通过抑制驱动偏析转变来进行热力学信息的LME缓解。结合原子模拟和先进的透射电子显微镜，将研究镀锌铁二元或三元模型合金，以i)系统地展示如何抑制偏析转变，ii)识别晶界开裂之前的初始晶界相，以及iii)量化特定合金元素如何削弱钢中的晶界。如果成功，该研究项目将为先进高强度钢中的LME提供一个基本的缓解策略。

Modern high-strength steels are a critical material class for infrastructure and the automotive sector. The ongoing development towards 3rd generation high-strength steels comes along with a decades-old problem: once galvanized (Zn coated) to passivate the steel, significant property deterioration can emerge if joined with methods that melt the Zn. Indeed, the co-existence of a liquid metal in contact with a solid substrate, here Zn and a steel, leads to embrittlement via grain-boundary phenomena and is referred to as liquid-metal embrittlement (LME). Being a pressing problem for industry, fundamental approaches are needed to understand and mitigate LME for modern steels. Based on our earlier work discovering nano-scale grain-boundary weakening intermetallic phase formation much prior to LME microcracking, and identifying a segregation transition as its cause, we set here out to conduct thermodynamically-informed mitigation of LME by suppressing the driving segregation transition. In combination with atomistic simulations and advanced transmission electron microscopy, galvanized Fe binary or ternary model alloys will be investigated, to i) systematically demonstrate how the segregation transition can be suppressed, to ii) identify initial grain-boundary phases prior to grain-boundary cracking, and to iii) quantify how specific alloying elements weaken grain-boundaries in the steel. If successful, this research project will provide a fundamental mitigation strategy for LME in advanced high-strength steels.