investigation of a new type of martensitic reversion from ferrite initial structure

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01729
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 26040:Structural materials and functional materials-related
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Nakada Nobuo 東京工業大学, 物質理工学院, 准教授 (50380580)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 鉄鋼材料 / 相変態 / マルテンサイト変態 / 逆変態 / 力学特性

Outline of Final Research Achievements

On the basis of an academic question, How microstructure does the austenite have via bcc-fcc reversion, if the initial bcc has no substructure?, the martensitic reversion formed from recrystallized bcc-ferrite was investigated. The analysis in terms of thermodynamics and kinetics found that the martensitic reversion takes place in Fe-16mass%Ni alloy under the continuous heating at 200 degree C/s. In addition, TEM observations proved that transformed microstructure is developed and high-density dislocations are introduced even through the bcc-fcc reversion.

Free Research Field

構造用金属材料

Academic Significance and Societal Importance of the Research Achievements

マルテンサイト変態と逆変態を繰り返す場合，変態温度に由来した駆動力の差異はあるものの，fcc（面心立方格子）とbcc（体心立方格子）のどちらを初期組織としても，その本質は変わらないことが明らかとなった．すなわち，室温での強靭化や高温での高強度化など，要求する力学特性に及ぼす変態下部組織の効果を考慮し，初期組織を選択することが鉄鋼材料を初めとする構造用金属材料の組織制御に重要であることが示唆される．