Mechanical Behavior of Ion-Irradiated Fe-Cr alloys Investigated by Spherical Indentation

Abstract

ABSTRACTFe12%Cr was irradiated with 2MeV and 0.5MeV Fe+ ions at 320°C, to create a layer with a mean level of displacement damage of 6.18dpa to a depth of ∼800nm. Spherical indentation, with a nominal tip radius of 10μm, was used to investigate the mechanical properties of the damage layer. Indents produced with loads of 2mN, 3mN, 5mN and 10mN were cross-sectioned and fabricated into TEM foils using an in situ lift-out technique in a dual beam FIB-SEM microscope. The extent of the plastic zone beneath the indent was observed in the TEM for each indentation. The indentation results were analysed so as to give an indentation stress-strain curve, in which strain softening was found to occur beyond the yield point. At loads up to 3mN the plastic zone remained entirely within the damage layer, implying strain-softening of the damaged material. At higher indentation loads the plastic zone was observed to extend into the softer un-irradiated substrate, giving rise to a further fall in flow stress with increasing strain.