Essential understanding of solute segregation at grain boundary in iron alloys by considering boundary coherency

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K14840
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Material processing/Microstructural control engineering
• Research Institution: Tohoku University
• Principal Investigator: ZHANG YONGJIE 東北大学, 金属材料研究所, 助教 (40793740)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 粒界偏析 / 粒界性格 / 合金元素 / アトムプローブ

Outline of Final Research Achievements

The effects of C and Mo additions on equilibrium grain boundary segregation behaviors of P in ferritic model alloys were investigated by using three-dimensional atom probe. In annealed Fe-P binary alloy, the segregation amount of P at high-angle grain boundary was found to be higher than that at low-carbon grain boundary. Based on this, the grain boundaries in C-added alloy and Mo-added alloy with similar boundary characters were selected for analysis. Even with small amount of addition, C is severely segregated at grain boundary, which reduces the segregation amount of P. On the other hand, the segregation amount of P is not changed by the segregation of Mo. The effects of these alloying elements can be understood by considering the thermodynamics in terms of their interactions with P.

Free Research Field

金属材料

Academic Significance and Societal Importance of the Research Achievements

フェライトのモデル合金におけるPの粒界偏析におよぼす粒界性格および合金元素添加の影響解明は、Pの粒界偏析に起因した実用マルテンサイト鋼の高温焼戻し脆性の抑制対策の確立に不可欠である。本研究の成果に基づいて、マルテンサイト鋼の結晶方位制御、またはC、Moなどの合金元素添加を活用することで、P含有の焼戻しマルテンサイト鋼の靭性向上が期待される。また、多成分系における粒界偏析挙動を元素間相互作用の観点で理解することは、他の合金系への展開も可能である。