Phase equilibria and thermodynamic analysis of anomalous microstructure formation at low temperatures by heavy deformation and heat treatment processes

2015 Fiscal Year Final Research Report

• Project/Area Number: 25289216
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Physical properties of metals/Metal-base materials
• Research Institution: National Institute for Materials Science (2015); Tohoku University
• Principal Investigator: OHNUMA IKUO 国立研究開発法人物質・材料研究機構, 理論計算科学ユニット, 主席研究員 (20250714)
• Co-Investigator(Kenkyū-buntansha): ISHIDA Kiyohito 東北大学, 工学研究科, 名誉教授 (20151368)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 相平衡 / 相変態 / CALPHAD / 鉄鋼材料 / 組織制御 / 状態図

Outline of Final Research Achievements

Fe-Mn and Fe-Ni alloys, which are important systems for steel materials, were powdered by a gas-atomize method. Then, the powder samples were severely deformed by a converge milling process and heat-treated at temperatures between 700℃ and 450℃ (below the melting point of pure iron) to obtain the γ(fcc)+α(bcc) microstructure. Equilibrium compositions of the γ and α phases at low temperatures were measured by FE-EPMA. As a result, it is suggested that the solubility of Mn and Ni in the αFe at temperatures below 600℃ is larger than that in the literature. Similar experiments were performed on the Fe-Al binary alloys to obtain A2/B2/D03 order-disorder immiscible microstructures. As a result, it is suggested that equilibrium compositions among A2, B2 and D03 phases depend on the coherency at the inter-phase boundaries. Al-rich portion of the phase diagram of the Fe-Al binary system was also determined in this research subject.

Free Research Field

材料組織学