Quantitative understanding on brittle fracture of martensitic steel based on microscopic plastic deformation behavior

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K21083
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 26:Materials engineering and related fields
• Research Institution: National Institute for Materials Science
• Principal Investigator: SHIBATA Akinobu 国立研究開発法人物質・材料研究機構, 構造材料研究拠点, グループリーダー (60451994)
• Project Period (FY): 2020-07-30 – 2022-03-31
• Keywords: 脆性破壊 / マルテンサイト鋼 / 塑性変形

Outline of Final Research Achievements

The present study investigated microscopic plastic deformation behavior accompanying fracture through scanning electron microscopy - electron backscattering diffraction(SEM-EBSD), digital image correlation(DIC) technique, and finite element simulation. For hydrogen-related intergranular fracture, the intense localization of plastic deformation around the crack tip was confirmed by SEM-EBSD. The hydrogen-related quasi-cleavage cracks formed at the surface of the notch root. The finite element simulations revealed that the plastic strains were maximum at the initiation sites of the quasi-cleavage cracks. Moreover, we confirmed by DIC technique that hydrogen enhanced the local plastic deformation. The relationship between martensite microstructure and plastic deformation behavior under tensile deformation was analyzed by DIC technique. The results suggested that plastic deformation was preferentially accumulated around the prior austenite grain boundaries.

Free Research Field

材料組織学

Academic Significance and Societal Importance of the Research Achievements

本研究では，マルテンサイト鋼の脆性破壊という具体的な現象において，その破壊過程におけるミクロスケール塑性変形挙動をSEM-EBSD解析，デジタル画像相関法，有限要素シミュレーションにより定量的に評価した．この結果は，破壊現象における原子スケール破壊特性 / ミクロスケールでの塑性変形挙動 / マクロ破壊特性の定量相関解明に関しての道筋を示したものであるため，破壊研究分野を飛躍的に発展させる契機となる可能性を十分に有していると言える．さらに脆性破壊を抑制するための材料組織制御法に繋がるため，耐破壊特性に優れた材料開発を通して，安全・安心な社会を構成するための社会基盤の構築に貢献しうるものである．