J. Phys. IV France
Volume 05, Numéro C7, Novembre 1995
Second International Conference on Ultra High Purity Base Metals
UHPM - 95
Page(s) C7-277 - C7-286
Second International Conference on Ultra High Purity Base Metals
UHPM - 95

J. Phys. IV France 05 (1995) C7-277-C7-286

DOI: 10.1051/jp4:1995733

Radiation-Induced α' Phase Formation on Dislocation Loops in Fe-Cr Alloys During Electron Irradiation

E. Wakai1, A. Hishinuma1, Y. Kato2, 3, H. Yano2, S. Takaki2 and K. Abiko2

1  Department of Materials Science and Engineering, JAERI, Tokai, Ibaragi 319-11, Japan
2  Institute for Materials Research, Tohoku University, Sendai, Miyagi 980, Japan
3  Technical Research Division, Kawasaki Steel Corporation, Chuo-ku, Chiba 260, Japan

Radiation-induced precipitates on dislocation loops in low and high purity Fe-9, -18 and -50 % Cr alloys were examined under electron irradiation in a high voltage electron microscope operated at 1 MV. Two types of dislocation loops on {100} planes with a <100> Burgers vectors and on {111} planes with a /2<111> are formed in high purity Fe-Cr alloys. However, only a <100> type loops are formed in low purity alloys, i.e. where carbon concentration is greater than about 60 wt.ppm. The growth rate of the loops formed in Fe-9 and -18Cr alloys is faster than that of Fe-50Cr alloy. All of the loops formed at temperatures ranging from 573 K to 973 K, even in the ( σ+α+α') phase regions in thermal equilibrium, have moiré fringe contrast due to precipitates identified as α' phase. The contrast is very weak in the Fe-50Cr alloy because of coarse distribution of precipitates, while the α' phase formed in low purity alloys has somewhat larger interplanar spacings that are modified by interstitial impurities. The α' phase formation on the loops can be understood by radiation-induced segregation of chromium and interstitial impurity atoms.

© EDP Sciences 1995