Enhancement of ductility by controlling three dimensional structure and retained austenite in steels

2018 Fiscal Year Final Research Report

• Project/Area Number: 17H04958
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Material processing/Microstructural control engineering
• Research Institution: The University of Tokyo
• Principal Investigator: Nambu Shoichi 東京大学, 大学院工学系研究科(工学部), 准教授 (00529654)
• Research Collaborator: KOSEKI toshihiko
• Project Period (FY): 2017-04-01 – 2019-03-31
• Keywords: 鉄鋼材料 / オーステナイト / その場観察 / 結晶塑性有限要素法 / 加工誘起マルテンサイト変態 / 3次元組織観察

Outline of Final Research Achievements

In order to achieve more improved strength and ductility combinations of new multi-phase steels with 3-dimensional continuous complicated structure, the microstructural morphology in the 3-dimensional structures was evaluated, and the relationship between the microstructure and mechanical properties was examined. By observing the 3-dimensional structure of martensite, it was shown that the effect of boundary planes on the microstructure is large in the early stage of the transformation. In addition, an in-situ observation and a stress field analysis using crystal plasticity finite element model were conducted for the deformation-induced martensite transformation of retained austenite, and it was demonstrated that the position where the deformation-induced martensite transformation onsets can be estimated.

Free Research Field

材料組織制御工学

Academic Significance and Societal Importance of the Research Achievements

３次元の組織形態評価は近年の測定装置の精度向上によってようやく評価可能になった研究領域であり，この評価技術によって得られる組織と力学特性の関連性を明確にすることは，鉄鋼材料に限らず今後の新規材料開発においても重要な役割を果たすと考えられる。また，残留オーステナイトの制御は，材料の加工硬化率を制御するという点において産業的に非常に重要であることに加えて，複雑応力場でのマルテンサイト変態の理解や結晶塑性有限要素法によるマルテンサイト変態挙動の予測は科学的にも非常に有益であると考えられる。