In Situ AFM Analysis of Surface Electron Behaviors of Strain‐Free and Deformed Ferrite and Austenite in Duplex Steel and Their Correlation with Electron Work Function

Abstract

Surface electron state and kinetic behavior as well as their spatial distributions strongly influence surface properties of microscopically inhomogeneous materials and related processes. Using a multi-mode atomic force microscope, electron work functions and surface electrical currents of ferrite and austenite in duplex steel are in situ analyzed. Along with slightly higher work function, the austenite shows higher electrical conductance than ferrite, which is consistent with first-principles calculations. Local plastic deformation introduced by micro-indentation results in considerable changes. The current around indents on austenite slightly increases along with lowered work function, while that around the indent on ferrite increases significantly accompanied with lowered work function. Efforts are made to understand mechanisms for the observed phenomena.

Characterization of the Native Passive Film on Ferrite and Austenite Phases of Sensitized 2205 Duplex Stainless Steel

“…Similarly, Sathirachinda et al showed that ferrite phase has a lower Volta potential than austenite phase, due to its lower Ni content and higher contents of Cr and Mo. 32,33 Volta potential or surface electron work function strongly affect the tendency of charge transfer and dissolution rate of material during exposure to corrosive media 60 and have a direct correlation with the electrochemical interactions and physical properties (stability and arrangements of atomic bonds and density of defects) of material in contact with solutions. The global work function of individual phases can be estimated to a first approximation based on their chemical composition following the procedure described previously, 61 using:…”

“…As tabulated in Table I, the estimated work functions are in the decreasing order of austenite > ferrite > chi and sigma. The presence of IMPs in the For in depth assessment of the Volta potential distributions over the entire scanned regions, we analyzed the Volta potential maps using the multi-modal Gaussian distribution model 58,60 and presented the results as histogram distributions, for solution annealed and sensitized samples in Figs. 5c and 5d, respectively.…”