Mechanical N. Adachi 1, K. Iwamoto 1 and Y. Todaka 1 1 Department of Mechanical Engineering, Toyohashi University of Technology It has been reported that ultrafine grained (UFG) materials shows not only high strength but also relatively large elongation. We previously investigated mechanical property of pure Fe having different grain sizes prepared by the high-pressure torsion and annealing processes1). We found that the UFG pure Fe shows noticeable uniform elongation. In order to understand the interesting mechanical behavior of UFG pure Fe, elementary process of dislocation motion in the UFG sample should be clarified. In this study, mechanical behavior of the UFG pure Fe samples with difference grain sizes was investigated. Then, strain rate jump test was performed under three different strain rates. From the magnitude of the difference of flow stress before and after a strain rate jump, activation volume for dislocation motion in each sample was evaluated. The obtained activation volumes were plotted as a function of true shear stress in a double logarithmic graph. The plot indicated that the activation volume varies in inverse proportion to the shear stress irrespective of initial grain size of the sample. This relation implies that the main obstacle for dislocation is forest dislocation, and dislocation density under tensile test became larger with decreasing grain size. It is interesting to note that the pure Fe having a grain size of the 1 µm or lower showed unique mechanical response at the timing of a strain jump; the overshoot and undershoot of stress. The cause of such mechanical response will be also discussed in this presentation. 1) N. Adachi, H. Sato, Y. Todaka, and T. Suzuki, Proc. Manuf. 15 (2018) 1495–1501. Construction of a M K.Kawagishi 1 and T. Osada 1 1Research Center for Structural The Ni-base superalloys developed by NIMS have the excellent temperature capability and can reduce CO2 emissions when applied to aircraft engines. However, practical application to aircraft engine materials requires collecting a lot of data and verifying safety. In order to strengthen the competitiveness of domestically produced superalloys, we will work with major domestic engine manufacturers to obtain material property data with the aim of obtaining certification from aviation authorities, and build a database that can be used within an all-Japan framework. Response of Pure Fe Having Different Grain Sizes under Tensile Stress aterials Database for Aeroengine MPoster Presentation ｜NIMS Award Symposium 2023 Materials, National Institute for Materials Science (NIMS) P2 ｜ Characterizationaterials PP22--2277 PP22--2288 57
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