2026年1月13日、Dr. Yuki Ikeda（BAM, Germany）によるご講演が第186回構材ゼミとして開催されました。
日時：2026年1月13日（火曜日）11:00-12:00
場所：NIMS千現地区 先進構造材料研究棟5階カンファレンスルーム
講演題目：Analysis of liquid-metal embrittlement of advanced high-strength steels by advanced transmission electron microscopy methods
講演者：Dr. Yuki Ikeda Postdoctoral researcher, Abteilung 5.0 Werkstofftechnik Bundesanstalt für Materialforschung und-prüfung (BAM), Germany
開催者：佐々木 泰祐（微細組織解析グループ）
講演後の集合写真
Dr. Yuki Ikeda（前列 右から4番目）
Abstract:
Liquid-metal embrittlement (LME) is a degradation phenomenon where liquid metal penetrates grain boundaries (GBs), lowering GB cohesion, then causing catastrophic failure. The LME in Fe-Zn system draws attention especially from automobile sectors because this phenomenon often hinders the implementation of newly developed steel grades. However, the embrittling mechanism, particularly the role of Zn inside a GB, is not yet fully understood.
In this talk, representative LME couples including Fe-Zn will be introduced, and then, our recent observations on the LME of 3rd-generation advanced high-strength steels (3rd gen. AHSSs) [1,2] will be showcased. By using transmission electron microscopy (TEM) and 4D-STEM, our study provides the first evidence of Fe-Zn LME driven by Fe-Zn compound formation. The experimental findings are further supported by thermodynamical simulations, suggesting that GB spinodal in a Fe high-angle GB (HAGB) could be the critical step of this LME [3,4]. The experimental validation for this GB spinodal is done by an in-situ heating TEM setup, demonstrating a presence of Zn in a HAGB could lead to localized Zn segregation within the GB plane and subsequent GB phase formation. These insights provide a pathway for designing LME-resistant AHSS via GB engineering. Lastly, our ongoing projects and collaborations will be briefly introduced.
References [1] Y. Ikeda et al., Materials Today Advances, 13(6), 100196 (2022).
[2] Y. Ikeda et al., Acta Materialia, 259, 119243 (2023).
[3] R. Darvishi Kamachali et al., Scripta Materialia, 238, 115758 (2023).
[4] Y. Ikeda et al., Acta Materialia, 296, 121134 (2025).