Heavy-ion irradiations of Fe and Fe–Cr model alloys Part 1: Damage evolution in thin-foils at lower doses

Abstract

The evolution of radiation damage in Fe and Fe–Cr alloys under heavy-ion irradiation was investigated using transmission electron microscopy. Thin foils were irradiated with 100 or 150 keV Fe⁺ and Xe⁺ ions at room temperature (RT) and 300°C. Dynamic observations followed the evolution of damage and the early stages in damage development are reported. Small (2–5 nm) dislocation loops first appeared at doses between 10¹⁶ and 10¹⁷ ions m⁻² in all materials. Loop number densities depended strongly on the foil orientation in pure Fe but not in Fe–Cr alloys. Number densities did not depend strongly on Cr content. For a given material, defect yields were higher for Xe⁺ ions than for Fe⁺ ions, and were higher at RT than at 300°C. Loops with both ⟨100⟩ and ½⟨111⟩ Burgers vectors were identified. The proportion of ⟨100⟩ loops was larger, especially in pure Fe. Dynamic observations showed that: the contrast of some new loops developed over intervals as long as 0.2 s; hopping of ½⟨111⟩ loops was induced by the ion and electron beams and was pronounced in ultra-pure iron; and many loops were lost during and after ion irradiation by glide to the foil surface. The number of loops retained was strongly dependent on the foil orientation in Fe, but less so in Fe–Cr alloys. This is due to lower loop mobility in Fe–Cr alloys, probably due to pinning by Cr atoms. Reduced loop loss probably explains the higher loop number densities in Fe–Cr alloys compared with pure Fe.

Keywords:

• radiation damage
• FeCr alloys
• in situ TEM

Acknowledgements

The IVEM-Tandem Facility (within the Electron Microscopy Center at ANL) is supported by the US DOE Office of Science and operated under contract no. DE-AC02-06CH11357 by UChicago Argonne, LLC. We thank Dr. A. Liu and P. Baldo of Argonne National Lab for their help in using this facility. Part of this work was funded by the UKAEA, Culham Science Centre. We thank Prof. J. Le Coze of the École de Mines de Saint Étienne for the provision of UHP iron. We are grateful to Dr. S.L. Dudarev, Dr. C.A. English and M. Gilbert for helpful discussions.

Notes

Note

1. In order to play these. mpg files with RealPlayer you may need to install an mpeg-2 video codec, which is widely available as a free download on the web.