The effect of strain on the impedance and surface potential of austenite in 304 stainless steels

Local electrochemical technique was used to measure the impedance of austenite in AISI 304 stainless steel under tensile strain of 0%, 10%, 20%, 30%, 40%. Scanning Kelvin probe (SKP) technique was used to measure the potential distribution of the surface. The results showed that the impedance of the austenite declined with the increase of the strain and declined sharply under the strain of 30%. Potential of austenite decreased non-monotonously with increase of the strain. The potential reached the minimum under strain of 30% and then increased. Through the transmission electron microscope (TEM) results, plane dislocation pile-ups were observed in the grain boundary under the strain of 30% and transformed to cellular substructure structure and cell wall under 40%. Combined with the results of local electrochemistry impedance spectroscopy (LEIS) and surface potential, it may be concluded that it was the dislocation density and dislocation structure influence the impedance spectroscopy significantly, while surface potential was sensitive to the dislocation structure.