Fabrication of Ultrafine Grained Austenitic Steel by Chemical Stability Controlled Phase Transformations

2014 Fiscal Year Final Research Report

• Project/Area Number: 24560852
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Structural/Functional materials
• Research Institution: Kyushu University
• Principal Investigator: NAKADA Nobuo 九州大学, 工学(系)研究科(研究院), 助教 (50380580)
• Co-Investigator(Kenkyū-buntansha): TANAKA Masaki 九州大学, 大学院工学研究院, 准教授 (40452809)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 鉄鋼材料 / 構造・機能材料 / 相変態 / 組織制御 / 超微細粒鋼

Outline of Final Research Achievements

For further strengthening of TWIP steel which is expected as a next generation automotive steel sheet, a new heat treatment to promote precipitation and dissolution of carbide was applied for Fe-Mn-C alloys, leading to grain refinement via phase transformations. As a result, it was confirmed that austenite matrix is unstabilized after (austenite + carbide) two phase austenitization, namely partial solution treatment, and the heat treatment stimulates martensitic transformation in austenitic steel without any cold-deformation. In addition, it was found that reversion mechanism is discontinuously shifted from diffusive type to martensitic one with increasing heating rate in low Mn steels.

Free Research Field

金属組織学、構造材料工学