ハイエントロピー合金の照射損傷

ハイエントロピー合金の照射損傷†

Figure 1 Schematic illustration of the model of the simplest type defect in multi-component alloys such as High Entropy alloys (HEAs) [4,8]

High-Entropy Alloys (HEAs) consists of multi-component materials with an approximately equiatomic ratio of components [1-3]. These alloys have a high entropy of mixing, which distinguishes them from conventional alloys. Solid solutions with multi-principal elements have generally been found to be more stable than intermetallic compounds at elevated temperatures because of their large entropies of mixing. Some researchers have defined a HE material as one that has at least five principal elements, each of which has an atomic concentration between 5% and 35%.
Multi-component alloys with equiatomic compositions, such as HEAs, have a potential to possess superior phase stability against irradiation damage because of the special defect structure and/or particular atomic level stress [4,5]. We investigate the irardiation damage in multi-component equimolar alloys (MEAs) and HEAs because these materials may be a new type of nuclear material that do not show irradiation damage problems because of faster irradiation damage annihilation and/or evaluation processes compared to conventional crystalline materials [6-8].

REFERENCES
[1] B. Cantor, I.T.H. Chang, P.K. Night, A. J. Vincent: Mater. Sci. Eng. A 375, (2004) 213-218.
[2] S. Ranganathan: Curr. Sci., 85 (2003) 1404-1406.
[3] J.W. Yeh, S.K. Chen, S.J. Lin, J.Y. Gan, T.S. Chin, T.T. Shun, C.H. Tsau, S.Y. Chang, Adv. Eng. Mater. 6 (2004) 299-303.
[4] T. Nagase, Advanced materials design by irradiation of high energy particles, Progress in Advanced Structural and Functional Materials Design, Ed., T. Kakeshita, Springer, 2012. pp. 137-153. ISBN 978-4-431-54063-2, http://www.springer.com/materials/structural+materials/book/978-4-431-54063-2
[5] T. Egami, W. Guo, P. D. Rack, T. Nagase, Metall. Mater. Trans. A, 45 (2014) 180-183., http://link.springer.com/article/10.1007/s11661-013-1994-2
[6] T. Nagase, S. Anada, P. D. Rack, J. H. Noh, H. Yasuda, H. Mori, T. Egami, Intermetallics, 26 (2012) 122-130., http://dx.doi.org/10.1016/j.intermet.2012.02.015
[7] T. Nagase, S. Anada, P. D. Rack, J. H. Noh, H. Yasuda, H. Mori, T. Egami, Intermetallics, 38 (2013) 70-79., http://dx.doi.org/10.1016/j.intermet.2013.02.009
[8] T. Nagase, P. D. Rack, J. H. Noh, T. Egami: Intermetallics, 59, 32-42 (2015)., http://dx.doi.org/10.1016/j.intermet.2014.12.007

ハイエントロピー合金の照射誘起アモルファス化†

Figure 1 Solid state amorphization in High Entropy alloys (HEAs) by fast electron irradiation [6]

High-entropy alloys (HEAs) have been developed as a new class of structural materials. Mixing of various elements typically results in high atomic-level stresses and particular defects that lead to the possibility of achieving high irradiation resistances through unique damage healing mechanisms [1]. The preliminary experimental results obtained from high-voltage electron microscopy (HVEM) focus on irradiation damage in various equiatomic multicomponent alloys and HEAs [2-6], and demonstrated that the ZrNbHf, CoCrFeNi and TiNbTaZr alloys, and the CoCrCuFeNi, Al0.3CoCrFeNi, and TiNbTaZrV HEAs remain in the solid solution under fast electron irradiation; on the other hand, the HEA Al0.5TiZrPdCuNi exhibited solid-state amorphization (SSA) [6].

REFERENCES
[1] T. Egami, W. Guo, P.D. Rack, T. Nagase, "Irradiation Resistance of Multicomponent Alloys", Metallurgical and Materials Transactions A, 45 (2014) 180-183., http://doi.org/10.1007/s11661-013-1994-2
[2] T. Nagase, S. Anada, P. D. Rack, J. H. Noh, H. Yasuda, H. Mori, T. Egami, "Electron-irradiation-induced structural change in Zr-Hf-x.Nb alloy", Intermetallics, 26 (2012) 122-130., http://doi.org/10.1016/j.intermet.2012.02.015
[3] T. Nagase, S. Anada, P. D. Rack, J. H. Noh, H. Yasuda, H. Mori, T. Egami, "MeV electron-irradiation-induced structural change in the bcc phase of Zr-Hf-Nb alloy with an approximately equiatomic ratio", Intermetallics, 38 (2013) 70-79., http://doi.org/10.1016/j.intermet.2013.02.009
[4] T. Nagase, P. D. Rack, J. H. Noh, T. Egami, "In-situ TEM observation of structural changes in nano-crystalline CoCrCuFeNi multicomponent high-entropy alloy induced under fast electron irradiation by high voltage electron microscopy", Intermetallics, 59, 32-42 (2015)., http://doi.org/10.1016/j.intermet.2014.12.007
[5] M-.R. He, S. Wang, K. Jin, H. Bei, K. Yasuda, S. Matsumura, K. Higashida, I.M. Robertson, "Enhanced damage resistance and novel defect structure of CrFeCoNi under in situ electron irradiation", Scripta Materialia, 125 (2016) 5-9., http://doi.org/10.1016/j.scriptamat.2016.07.023
[6] T. Nagase, A. Takeuchi, K. Amiya, T. Egami, Materials Chemistry and Physics, 210, 291-300 (2018)., "Solid State Amorphization of Metastable Al0.5TiZrPdCuNi High Entropy Alloy Investigated by High Voltage Electron Microscopy", http://doi.org/10.1016/j.matchemphys.2017.07.071