Heavy-ion Irradiations of Fe and Fe-Cr Model Alloys Part 1: Damage evolution in thin-foils at lower doses

Zhongwen Yao (1) , Mercedes Hernández-Mayoral (2) , Mike Jenkins (1) , Mark Kirk (3)

1 Materials
2 Division of Materials
3 MSD - Material Science Division [ANL]

The evolution of radiation damage in Fe and FeCr alloys under heavy-ion irradiation has been investigated by TEM. Thin foils were irradiated with 100 or150 keV Fe+ and Xe+ ions at room temperature and 300oC. Dynamic observations followed the evolution of damage. We report on early stages in damage development. 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 FeCr 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 300oC. 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: (1) the contrast of some new loops developed over intervals as long as 0.2s; (2) hopping of ½ <111> loops was induced by the ion and electron beams and was pronounced in ultra-pure iron; and (3) 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 FeCr alloys. This is due to a lower loop mobility in FeCr alloys probably due to pinning by Cr atoms. Reduced loop loss probably explains the lower loop number densities in FeCr alloys compared with pure Fe.

Mots clés: Physical Sciences

Zhongwen Yao, Mercedes Hernández-Mayoral, Mike Jenkins, Mark Kirk. Heavy-ion Irradiations of Fe and Fe-Cr Model Alloys Part 1: Damage evolution in thin-foils at lower doses. Philosophical Magazine, 2008, 88 (21), pp.2851-2880. ⟨10.1080/14786430802380469⟩. ⟨hal-00513952⟩