【公開日：2025.06.10】【最終更新日：2025.05.09】
課題データ / Project Data
課題番号 / Project Issue Number
24TU0088
利用課題名 / Title
脱合金法による複合材料の開発
利用した実施機関 / Support Institute
東北大学 / Tohoku Univ.
機関外・機関内の利用 / External or Internal Use
内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）次世代ナノスケールマテリアル/Next-generation nanoscale materials（副 / Sub）-
キーワード / Keywords
ナノコンポジット材料/Nano composite,集束イオンビーム/ Focused ion beam
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
唐 博聞
所属名 / Affiliation
東北大学金属材料研究所
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
竹中佳生
利用形態 / Support Type
（主 / Main）技術代行/Technology Substitution（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
This research aims to elucidate the detailed microstructural evolution and deformation mechanisms in Fe–Mg heterostructured composites fabricated by liquid metal dealloying (LMD). Specifically, we investigated the formation of nanoscale intermetallic MoFe₂ ligaments embedded within a Mg matrix and micron-scale bcc Fe ligament structure.
Focused Ion Beam (FIB) milling was employed for the precise preparation of thin TEM lamellae, enabling detailed structural and crystallographic analyses. Transmission Electron Microscopy (TEM) was utilized to characterize the nano- and atomic-scale structures of the as-prepared composites and their deformation-induced microstructures, including lattice distortions, dislocation structures, stacking faults, and phase interfaces. The study leverages high-resolution TEM imaging, selected area electron diffraction (SAED), and energy-dispersive X-ray spectroscopy (EDS) mapping to identify phase compositions, crystallographic orientations, and elemental distributions at the nanoscale. Through these analyses, the roles of nanoscale MoFe₂ ligaments and the interfaces between hard and soft zones in enhancing mechanical performance are systematically clarified. Results from this study offer valuable insights into deformation behaviors and strengthening mechanisms in novel heterostructured composites, contributing significantly to the fundamental understanding and future development of lightweight, high-strength materials for automotive and aerospace applications.
実験 / Experimental
Thin TEM samples were precisely prepared from bulk Fe–Mg heterostructured composites using a Focused Ion Beam (FIB, FEI Versa 3D) system. Initially, specimens were mechanically polished to remove surface contamination. The region of interest was identified using scanning electron microscopy (SEM), and a platinum protective layer was deposited in situ to prevent ion-beam damage during milling. A gallium (Ga) ion beam was then employed at progressively decreasing currents from 30 nA to 50 pA, to minimize damage and achieve the desired lamella thickness (<100 nm). Final thinning and cleaning steps at low ion currents (below 50 pA) were applied to further remove surface amorphization and minimize artifacts induced by ion milling. Transmission Electron Microscopy (TEM, FEI Titan G2) was performed at an accelerating voltage of 300 kV. High-angle annular dark-field (HAADF) imaging, high-resolution transmission electron microscopy (HRTEM), and geometric phase analysis (GPA) were conducted to reveal atomic-scale lattice distortions and interface characteristics.
Additionally, EDS mapping was performed to precisely identify the elemental distributions and compositions of Fe, Mo, Ni, and Mg at interfaces and within individual ligament phases. Selected-area electron diffraction (SAED) was utilized for crystal phase identification and orientation analysis, providing comprehensive structural insights into deformation-induced microstructural features and phase transformations.
結果と考察 / Results and Discussion
TEM analyses revealed the detailed microstructural characteristics of the heterostructured Fe–Mg composites. HAADF imaging clearly identified nanoscale MoFe₂ ligaments (~30 nm diameter) uniformly embedded within a continuous Mg matrix and larger-scale bcc Fe ligaments. High-resolution atomic imaging and GPA analyses demonstrated significant lattice distortions, stacking faults, and localized high-density dislocation regions within MoFe₂ ligaments after tensile deformation. These stacking faults were preferentially aligned perpendicular to the c-axis of the C14-type hexagonal Laves-phase structure, indicating that plastic deformation in MoFe₂ is primarily accommodated by stacking fault formation and limited twinning events. The interface regions between Mg, Fe, and MoFe₂ ligaments exhibited pronounced strain accumulation, as clearly revealed by GPA strain mapping. Such interfacial strain concentrations indicate strong interactions and effective dislocation pinning at phase boundaries, significantly contributing to the overall strengthening effect observed in mechanical tests. EDS elemental maps confirmed uniform distribution of Mo and Fe in nanoscale ligaments, consistent with their intermetallic MoFe₂ phase composition. These findings demonstrate the critical roles played by nanoscale intermetallic ligaments and immiscible interfaces in determining the enhanced strength–ductility synergy of the heterostructured composites. These TEM-derived insights into atomic-scale deformation mechanisms and microstructural evolution provide essential guidance for the future microstructural tailoring and mechanical property optimization of lightweight metal–matrix composites.
図・表・数式 / Figures, Tables and Equations
Fig. 1. Preparation of TEM specimen using FIB technique: thinning process of Fe–Mg composite.
Fig. 2. HAADF images, elemental distribution maps, and corresponding selected area electron diffraction (SAED) patterns of the Fe–Mg composite prepared by liquid metal dealloying (LMD).
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
The authors gratefully acknowledge the technical support provided by Kana Takenaka and Yuichiro Hayasaka from Tohoku University for their invaluable assistance with the FIB sample preparation and TEM observation, respectively. Their contributions have been essential to the successful completion of this research.
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
- Bowen Tang, "Immiscible Fe／Mg Bicontinuous Composites with Nano MoFe2 by Liquid Metal Dealloying" 日本金属学会第 175 回大会, 令和6年9月20日
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件