Grain refinement of steels by conroling strain field associated with displacive transformation

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04532
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Material processing/Microstructural control engineering
• Research Institution: Tohoku University
• Principal Investigator: MIYAMOTO GORO 東北大学, 金属材料研究所, 准教授 (60451621)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: せん断型変態 / マルテンサイト / ベイナイト / バリアント

Outline of Final Research Achievements

We have investigated effects of various factors on variant structure of martensite and bainite in ferrous alloys. We found that strong variant selection occurs in the nucleation of bainite at austenite grain boundary, which cause the formation of coarse grain boundary structure especially for in low carbon steel. Increase in carbon content, self-accommodation is enhanced and the formation of coarse grain boundary bainite structure is suppressed.
On the other hand, thickness and length of martensite are reduced at higher carbon content. Block length is decreased at smaller austenite grain size while effects of austenite grain size on block thickness is small.

Free Research Field

金属材料

Academic Significance and Societal Importance of the Research Achievements

マルテンサイトやベイナイト組織は高強度鋼に用いられる微細組織であり，これらの変態組織の微細化により，高い強度と高い靱性を兼ね備える材料の開発が可能となり，これらの材料を利用する輸送機器や機械構造部品の軽量化や長寿命化，信頼性向上に資する．本研究の成果は，これらの組織微細化の基本方針を示すものであり，合金組成や処理条件の最適化に寄与する．