The factors which controlled radiation hardening, and their contribution to the hardening of electron-irradiated pure Fe and Fe-0.15wt%Cu, were determined by using post irradiation-annealing hardness measurements, positron annihilation spectroscopy, transmission electron microscopy and 3-dimensional atom probe analysis. In pure Fe, almost complete recovery of the hardness was observed after annealing to 773K; accompanied by disappearance of interstitial-type dislocation loops (I-loops) that were observed in as-irradiated specimens. The hardness of Fe-0.15wt%Cu recovered in 2 steps: about half of the hardening recovered during 773K annealing, and complete recovery was observed after annealing to 973K. Most of the I-loops observed in as-irradiated specimens disappeared again after annealing to 773K. This clearly showed that the I-loops were one of the main factors which controlled irradiation hardening in Fe-Cu alloy. The residual hardening in Fe-0.15wt%Cu, after annealing to 773K (which was about half of the irradiation hardening), was attributed to Cu-rich precipitates. Positron annihilation spectroscopy measurements revealed a disagreement between the recovery behaviors of the hardness and lifetime parameters. It was concluded that the factor which controlled the irradiation hardening of pure Fe was the presence of I-loops. The important factor in Fe-0.15wt%Cu was the presence of both I-loops and Cu-rich precipitates; whose contributions to hardening were almost same.

Factors Controlling Irradiation Hardening of Iron-Copper Model Alloy. T.Kudo, R.Kasada, A.Kimura, K.Hono, K.Fukuya, H.Matsui: Materials Transactions, 2004, 45[2], 338-41