Radiation-induced precipitates on dislocation loops in low-purity and high-purity alloys were examined by means of high-voltage electron microscopy. Dislocation loops on {100} planes, with a<100> Burgers vectors, and on {111} planes with a/2<111> Burgers vectors, were formed in high-purity alloys. However, only a<100>-type loops formed in low-purity alloys; that is, when the C concentration was greater than about 60ppm[wt]. The growth rate of the loops which formed in the 9 and 18%Cr alloys was higher than that in the 50%Cr alloy. All of the loops formed at temperatures that ranged from 573 to 973K. The moiré contrast was very weak in the 50%Cr alloy because of the coarse distribution of the precipitates. The ’ phase which formed in low-purity alloys had a somewhat larger interplanar spacing, that was modified by interstitial impurities. The ’ phase formation on loops was explained in terms of the radiation-induced segregation of Cr and interstitial impurity atoms.

E.Wakai, A.Hishinuma, Y.Kato, H.Yano, S.Takaki, K.Abiko: Journal de Physique III, 1995, 5[7], 277-86