Martensite hardening mechanism in high carbon steels based on a new principle

2019 Fiscal Year Final Research Report

• Project/Area Number: 15H02304
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Structural/Functional materials
• Research Institution: National Institute for Materials Science
• Principal Investigator: PING Dehai 国立研究開発法人物質・材料研究機構, 構造材料研究拠点, 主幹研究員 (80354207)
• Co-Investigator(Kenkyū-buntansha): 阿部 太一 国立研究開発法人物質・材料研究機構, 構造材料研究拠点, 主幹研究員 (50354155) ; 大沼 正人 北海道大学, 工学研究院, 教授 (90354208)
• Project Period (FY): 2015-04-01 – 2020-03-31
• Keywords: 鉄鋼材料 / 炭素鋼 / TEM / 相変態

Outline of Final Research Achievements

No carbon, iron is iron. Iron with carbon becomes steel. Thus, it is very important to understand the role of carbon in steels. Understanding the role of carbon atoms in the microstructural evolution of carbon steels has been a key point in developing new steels. In about 100 years before this research project, it had been commonly accepted that the carbon atoms are in body-centered cubic (BCC) Fe to form a single crystal of Fe(C) martensite. Martensite is a hard structure. However, we have observed there are two crystalline phases (BCC-Fe and hexagonal ω-Fe in the Fe-C martensite. The ω-Fe is only distributed in the twinning boundary region. Based on this new finding, we started this research project. we have confirmed that the ω-Fe phase really exists together with BCC-Fe in Fe-C martensite, and have explained the formation mechanism, and also confirmed that the ω-Fe is the precursor of well-known cementite.

Free Research Field

鉄鋼材料

Academic Significance and Societal Importance of the Research Achievements

新たに発見した「鉄鋼中のオメガ相の形成」という視点から焼き入れ硬化現象について新原理の構築しました。鉄鋼材料研究の新しい方向性を切り拓き、21世紀の技術基盤となる新たな鉄鋼材料学を構築する。炭素鋼は、ごく一般的な汎用鉄鋼材料であり、鉄鋼材料として最もよく使われている。その中において、Fe-C合金は、典型的な二元合金炭素鋼である。また、炭素は、炭素鋼の性質に最も影響するため、熱処理時の炭素鋼中における炭素の挙動に関する研究は、多くの研究者の興味を引いている。