Characterization of Phases in Duplex Stainless Steel by Magnetic Force Microscopy/Scanning Kelvin Probe Force Microscopy

Abstract

A 2205 duplex stainless steel, which had undergone a slow cooling process in order to precipitate intermetallic phases, was characterized by means of magnetic force microscopy (MFM) and scanning Kelvin probe force microscopy (SKPFM), in addition to conventional scanning electron microscope and energy-dispersive spectroscopy analysis. MFM measurements yield information about the magnetic domain distribution, while SKPFM provides the variation in Volta potential between austenite , ferrite , and sigma phases . In general, paramagnetic austenite exhibits the highest Volta potential, followed by nonmagnetic sigma phase and ferromagnetic ferrite, respectively. Results show the applicability of MFM/SKPFM techniques for characterization of the individual phase properties of duplex stainless steel. Because a cross talk between magnetic and Volta potential signals has been observed, it is recommended to perform SKPFM measurements with nonmagnetic tips.