On determining the effect of surface-active elemental segregation on the oxide/metal interface: Atomic-scale analysis via HR-TEM

A mechanism for the effect of a surface-active element, namely Sb, on the bonding between an external oxide layer and a ferrous substrate was determined. It was found that Sb segregation at the external oxide/substrate interface resulted in decreased stability of the interfacial region. This was attributed to an increase in the atomic spacing near the interface in the Fe-xMn-0.03Sb (at%) alloys arising from Sb segregation, which led to the development of significant interfacial strains. The local strain reduced the energy required to separate the oxide from the metal matrix. HR-TEM revealed that this effect was intensified with increasing alloy Mn content, where the strain near the interface increased from 0.11 to 0.22 as the alloy Mn increased from 2 to 10 at.%. This was due to the higher bulk Mn content resulting in increased Sb segregation, which resulted in greater local strain in the interfacial region.