Dynamic Phase Transformation above Equilibrium Transformation Temperature in Steels

2014 Fiscal Year Final Research Report

• Project/Area Number: 26630365
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Material processing/Microstructural control engineering
• Research Institution: Kyoto University
• Principal Investigator: TSUJI Nobuhiro 京都大学, 工学(系)研究科(研究院), 教授 (30263213)
• Project Period (FY): 2014-04-01 – 2015-03-31
• Keywords: 鉄鋼材料 / 加工熱処理 / 動的変態 / 微細粒フェライト / 中性子回折

Outline of Final Research Achievements

Dynamic ferrite transformation behavior was investigated in a wide temperature range using 6Ni-0.1C and 2Mn-0.1C steels. Softening in flow stress due to dynamic transformation was observed at temperatures above Ae3 in both steels. Microstructural observation revealed that ferrite grains formed at temperature above Ae3 showed deformation microstructures, and those grains were reversely transformed to austenite during subsequent holding at the same temperature. Therefore, we concluded that dynamic ferrite transformation could certainly occur even above Ae3. In-situ neutron diffraction experiments during the hot-deformation under the same conditions as mentioned above was carried out using a thermomechanical processing simulator settled at BL 19 TAKUMI in J-PARC, but the dynamic transformation could not be clearly confirmed because of the limitation of time resolution in the neutron diffraction experiment.

Free Research Field

金属材料学、材料組織学、材料強度学