Transmission electron microscopy crystal structure analysis of G-phase precipitates in an overlay-clad duplex stainless steel on a light-water pressure vessel steel
Matsukawa, Yoshitaka*; Kakubo, Yuta*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Takeuchi, Tomoaki ; Yamaguchi, Yoshihito ; Katsuyama, Jinya ; Nishiyama, Yutaka
The / duplex stainless steel overlay-welded on the inner wall of light-water reactor pressure vessels for protection from corrosion is known to exhibit a complex phase transformation under thermal aging. Our atom-probe tomography analysis revealed that in the -ferrite /' spinodal decomposition and precipitation of nanometer-sized Ni-Mn-Si clusters occur together at 673 K after 2000 hrs. The Ni-Mn-Si clusters visualized in the 3-D atom map are most likely G-phase, which is an intermetallic compound commonly observed in this type of duplex stainless steels; however, since crystallographic information is largely lost in atom-probe data, it is unknown if they are certainly G-phase accompanied with a specific supper-lattice structure or simple agglomerates of solute atoms without any crystal structure change. In the present study crystal structure of the Ni-Mn-Si nano-clusters has been analyzed by transmission electron microscopy to determine the fraction of G-phase over all clusters.