Unified understanding of local deformation and deformation induced transformation for high strength steel

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15279
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26010:Metallic material properties-related
• Research Institution: Osaka University (2020); Japan Atomic Energy Agency (2019)
• Principal Investigator: Yamashita Takayuki 大阪大学, 接合科学研究所, 助教 (20829080)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 中性子回折 / 加工誘起変態 / リューダース変形 / TRIP効果 / 高強度鋼板 / 加工硬化 / 結晶方位 / 応力分配

Outline of Final Research Achievements

Deformation induced martensitic transformation behavior of austenite in medium Manganese steels during local deformation was investigated using in situ neutron diffraction during tensile test combined strain distribution measurement by digital image correlation and temperature measurement by infrared-ray thermography. The test steels showed local deformation after yielding and high work hardening rate. The most of austenite transformed to martensite regardless of their orientation with the passage of local deformation. After local deformation, austenite has almost no contribution to the strength due to the decrease in the phase fraction. The stress contribution of deformation induced martensite become large at later stage of deformation, thus the martensite may contribute to enhance the work hardening rate of the test steel.

Free Research Field

鉄鋼材料学

Academic Significance and Societal Importance of the Research Achievements

本研究を通して得られた結果は、中Mn鋼の複雑な変形挙動とそれに対する加工誘起相変態挙動の影響を理解していく上での基礎的な知見として資するものである。また、引張変形中その場中性子回折法に局所変形の同定法を組み合わせた本研究の手法は、中Mn鋼に限らず、局所変形中に生じる変形挙動や相変態挙動を解明するための強力なツールとなり得るため、中性子科学や鉄鋼材料学の今後の発展に寄与できると考える。