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The crystal structure evolution of the Cu-rich nano precipitates from bcc to 9R during thermal aging was studied in nuclear reactor pressure vessel(RPV)model steels.The specimens,contained higher copper and nickel contents than commercially available one,were heated at 890 C for 0.5 h and then water quenched followed by tempering at 660 C for 10 h and aging at 400 C for 1000 h.It was observed that bcc and 9R orthogonal structure,as well as 9R orthogonal and 9R monoclinic structure,coexist in a single Cu-rich nano precipitate.Further analyses pointed out that Cu-rich nano precipitates of bcc structure were not stable,it may preferentially transform to 9R orthogonal structure and then to 9R monoclinic structure.This results showed that the crystal structure evolution of the Cu-rich nano precipitates was complex.
The crystal structure evolution of the Cu-rich nano precipitates from bcc to 9R during thermal aging was studied in nuclear reactor pressure vessel (RPV) model steels. The specimens, contained higher copper and nickel contents than commercially available one, were heated at 890 C for 0.5 h and then water quenched followed by tempering at 660 C for 10 h and aging at 400 C for 1000 h. It was observed that bcc and 9R orthogonal structures, as well as 9R orthogonal and 9R monoclinic structures, coexist in a single Cu -rich nano precipitation. Further analyzes pointed out that Cu-rich nano precipitates of bcc structure were not stable, it may preferentially transform to 9R orthogonal structure and then to 9R monoclinic structure. This result showed that the crystal structure evolution of the Cu-rich nano precipitates was complex.