A nanostructured ferritic alloy (NFA), in the form of thin-walled tubing, was fabricated by hydrostatic extrusion of a mandrel mounted mother tube cut from a plate. The plate was processed by high energy ball milling of Fe-Y-Ti-O gas atomized and FeO powders, consolidated by hot extrusion, followed by hot cross rolling. The tube microstructure is dominated by an ultrahigh density of nm-scale Y-Ti-O complex oxide precipitates. Here, we examine the stability of the nano-oxides (NOs) under 3.5 MeV Fe +2 irradiations up to a peak dose of 1100 dpa at 450 °C. Transmission electron microscopy (TEM) and atom probe tomography (APT) show that severe ion irradiation may result in a slight decrease in the average diameter and increase in the number density of the NOs. This 'inverse coarsening' can be rationalized by the competition between radiation driven ballistic dissolution and diffusional NO reformation. No significant changes in the composition of the matrix or NOs were observed after irradiation. Modeling the experimental results also indicated a slight dissolution of the particles.

2017-08-30T02:06:54