Position Annihilation Study of Electron-Irradiated Fe-Cu Alloys

概要

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It is well known that the recovery of defects in iron alloys is affected by impurity atoms. Especially, the embrittlement process after high energy neutron irradiation in low alloy ferritic steels could be strongly influenced by small amount of impurity copper atoms. Fundamental process of this effect was studied by positron lifetime measurements with isochronal annealing in three series of Fe-Cu alloys of copper concentrations 0.02wt. %, 0.22wt. % and 0.05wt. % after 28MeV electron irradiation at 77K. The maximum value of positron lifetime \tau2 was about 280psec in Fe-0.02wt. % Cu, and about 190psec in Fe-0.22wt. % Cu, which was much smaller than that of pure iron (450psec). This showed that the vacancy cluster (microvoid) formation was disturbed as the concentration of copper atoms increased, and the vacancy migration temperature in Fe-Cu alloys was about 280K, which is higher than that of in pure iron1)2). It was also observed that the positron lifetime certainly decreased in higher temperature region in all alloys, which differs from other positron lifetime measurement data of various binary iron alloys, i.e. obtained by Corbel et al2)3).
1992-03-01