Direct In-Situ Investigation of Selective Surface Oxidation During Recrystallization Annealing of a Binary Model Alloy

Abstract

The study of high temperature oxidation processes depends mainly on ex situ investigations after the high temperature process is completed. In this study Ambient Pressure Photoelectron Spectroscopy was used to investigate its potential for an in situ analysis of the underlying mechanisms of selective oxidation occurring during high temperature annealing. As an example, the evolution of the surface oxide states of an iron-manganese model alloy (with 2 wt% Mn) during an annealing step simulating recrystallization annealing was studied. It was shown that an investigation of the surface after the annealing step does not provide reliable information about the oxidation state during the annealing step. At low partial pressures of water in a forming gas atmosphere the kinetics of water dissociation on the surface are not high enough to provide enough oxygen for reaching the thermodynamically expected activities. This unexpected low oxygen activity on the surface is also shown to affect the uptake of hydrogen into the Fe–2Mn sample.