Energy-resolved small-angle neutron scattering from steel

Oba, Yojiro*; Morooka, Satoshi; Oishi, Kazuki*; Suzuki, Junichi*; Takata, Shinichi; Sato, Nobuhiro*; Inoue, Rintaro*; Tsuchiyama, Toshihiro*; Gilbert, E. P.*; Sugiyama, Masaaki*

Journal of Applied Crystallography, 50(2), p.334 - 339, 2017/04

https://doi.org/10.1107/S1600576717000279

Quantitative evaluation of microstructure in metal by using Anomalous Small-Angle X-ray Scattering (A-SAXS) technique

Konno, Azusa; Yamashita, Shinichiro; Kumada, Takayuki; Oba, Yojiro; Motokawa, Ryuhei; Morooka, Satoshi; Ukai, Shigeharu*; Hashimoto, Naoyuki*; Ono, Naoko*; Shobu, Takahisa; et al.

no journal, , 

Duplex stainless steels is composed by austenite and ferrite phases, offering superior toughness, high strength properties, good weldability, and corrosion-resistance. It has been used as the heat exchanger components for the chemical industrial plants and pipes for the Pressurized light-Water Reactors (PWR). However, the duplex stainless steels is also known to suffer from the embrittlement due to the phase separation into the Cr-rich phase and Fe-rich one when it is annealed at longer time at the temperature over 300 degrees. In this study, we focused on the Anomalous Small-Angle X-ray Scattering (A-SAXS) technique that can analyze "arbitrary element" by using absorption edge of a specific element and estimated the chromium separation quantitatively by utilizing the A-SAXS method, considering the availability of this new technique as the quantitative and non-destructive analysis method for microstructure in metallic material.

Novel qualitative evaluation method of microstructure in ODS alloy by anomalous small-angle X-ray scattering technique

Konno, Azusa; Oba, Yojiro; Tominaga, Aki; Morooka, Satoshi; Ono, Naoko*; Hashimoto, Naoyuki*; Ukai, Shigeharu; Owada, Kenji*; Motokawa, Ryuhei; Kumada, Takayuki; et al.

no journal, , 

An ODS alloy is one of the promising candidate materials applicable to the fusion reactor because of its high-temperature creep strength and irradiation resistance. However, the ODS ferritic stainless steel with high Cr content sometimes suffers from the embrittlement related to phase separation below 748 K for a long term using in the reactor. It is, therefore, an important issue to understand embrittlement phenomena from not only macrostructural viewpoint but also microstructural one. Anomalous Small Angle X-ray Scattering (A-SAXS) is a unique and potential evaluation method that can analyze complex microstructure. This method can extract the signal only from an element of interest to implant the X-ray of the wavelength near orbit electron of the element. In this study, we performed both the A-SAXS analysis and TEM observation for high Cr-ODS alloy in order to assess the applicability of the A-SAXS technique as a microstructure determination and compared the A-SAXS signal with the TEM micrograph. The specimen of the commercial MA956 (Fe-20Cr-4.8Al-0.4Ti-0.02C-0.4YO (mass%)) were thermally-aged at 748 K for 1, 10, 100 and 1000 hrs, and measured using the A-SAXS diffractometer at BL22XU in SPring-8 and a TEM. The A-SAXS data reveal that the average size of Cr precipitations increases with increasing the aging time. Also, using the A-SAXS profiles, it was estimated that there were two cases; one is the case that the microstructure does have a distinct interface between the matrix and Cr precipitate. The other case is the microstructure does not have the distinct interface. On the other hand, in TEM observation, the periodic modulated structure was observed for 10 hrs thermally-aged sample, and the sphere precipitation was confirmed for 100 hrs thermally-aged sample. It was suggested that there would be a crucial phase separation mode from spinodal decomposition to nucleation-growth between 10 and 100 hrs.