Plastic zone size for nanoindentation of irradiated Fe-9%Cr ODS

The objective of this study is to determine irradiation effects on the nanoindentation plastic zone morphology in a model Fe-9%Cr ODS alloy. Specimens are irradiated to 50 displacements per atom at 400°C with Fe++ self-ions or to 3 dpa at 500°C with neutrons. The as-received specimen is also studied as a control. The nanoindentation plastic zone size is calculated using two approaches: (1) an analytical model based on the expanding spherical cavity analogy, and (2) finite element modeling (FEM). Plastic zones in all specimen conditions extend radially outward from the indenter, ∼4-5 times the tip radius, indicative of fully plastic contact. Non-negligible plastic flow in the radial direction requires the experimentalist to consider the plastic zone morphology when nanoindenting ion-irradiated specimens; a single nanoindent may sample non-uniform irradiation damage, regardless of whether the indent is made top-down or in cross-section. Finally, true stress-strain curves are generated.