The Effect of Short-Range Order on Passivation of Fe-Cr Alloys

While it is well known that 12–13 at.% chromium is required for stainless-like passivation behavior of binary Fe-Cr alloys, there remain outstanding questions regarding the compositional dependence of this behavior. In order to explore these issues, we examined the passivation behavior of short-range ordered (SRO) Fe-Cr alloys and compared this to that of their random solid solution counterpart. Our results reveal that for alloys containing between 12–18 at.% Cr, passivation in the SRO alloys is delayed and we attribute this to ordering effects on percolation behavior. Finally, we discuss some major outstanding questions regarding passivation in the Fe-Cr system and suggest that first-principles based calculations could make important contributions to our understanding of passivation in this system.