Establishment of novel strengthening principle of steels by spinodal ordering of light elements

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H01330
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Material processing/Microstructural control engineering
• Research Institution: Tohoku University
• Principal Investigator: Furuhara Tadashi 東北大学, 金属材料研究所, 教授 (50221560)
• Co-Investigator(Kenkyū-buntansha): 佐藤 充孝 東北大学, 金属材料研究所, 助教 (10547706) ; 張 咏ジエ 東北大学, 金属材料研究所, 助教 (40793740) ; 宮本 吾郎 東北大学, 金属材料研究所, 准教授 (60451621) ; 大谷 博司 東北大学, 多元物質科学研究所, 教授 (70176923)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 結晶・組織制御 / 時効析出

Outline of Final Research Achievements

Focusing on the interaction between interstitial and substitutional elements, the clustering behaviors by competition and coupling of ordering and phase separation during tempering of carbon/nitrogen martensite and nitriding process were investigated experimentally and theoretically. With the addition of substitutional elements, the kinetics of low-temperature tempering of high-carbon martensite was found to be delayed, while the resistance to temper softening occurs due to the formation of alloy carbide/nitride and nano-cluster, as well as the suppression of dislocation recovery. Moreover, the clustering behavior inducing the formation of nitride can enhance surface hardening during nitriding process. Such a precipitation sequence was reproduced by the combination of first-principles thermodynamics and kinetic Monte Carlo calculation.

Free Research Field

金属材料

Academic Significance and Societal Importance of the Research Achievements

スピノーダルオーダリングの概念に基づくマルテンサイトの低温焼戻しは、従来の機械構造用鋼での熱処理の意義を大きく覆し、ナノ合金炭窒化物の析出強化を用いる自動車用薄鋼板の分野でも新しい強化原理を提供する。また、窒化処理によるスピノーダルオーダリングを利用することで、機械部品/金型の耐摩耗性を飛躍的に向上させるポテンシャルがある。さらに、この理論を他の合金系へ展開することで、金属材料全般の特性改善が期待される。