Compression of self-ion implanted iron micropillars

Ion implantation causes displacement damage in materials, leading to the formation of small dislocation loops and can cause changes to the material’s mechanical properties. Samples of pure Fe were subjected to Fe+ implantation at 275 °C, producing damage of ∼6 dpa to ∼1 μm depth. Nanoindentation into implanted material shows an increase in hardness compared to unimplanted material. Micropillars were manufactured in cross-section specimens of implanted and unimplanted material and compressed using a nanoindenter. The implanted pillars have a deformation mode which differs markedly from the unimplanted pillars but show no change in yield-stress. This suggests that the controlling mechanism for deformation is different between nanoindentation and micropillar compression and that care is needed if using micropillar compression to extract bulk properties of irradiated materials.

► Self-ion implantation used to cause cascade damage in pure iron.
► Increase in hardness measured in implanted region using nanoindentation.
► Micropillars manufactured and tested in both implanted and unimplanted material.
► Marked difference in deformation mechanisms in each set of pillars seen using scanning electron microscopy.
► No difference in yield stress seen, suggesting it is difficult to use micro-compression to understand bulk properties.