Determination of retained austenite in multiphase steels by magnetic force microscopy

The use of atomic force microscopy (AFM) in the magnetic force mode (MFM) for the determination of austenite (non-magnetic phase) in duplex and TRIP (transformation-induced plasticity) steels is described. The influence of the sample preparation for the MFM measurements is investigated, showing that a final electropolishing stage is necessary in the case of TRIP-steels. The results of the determination of austenite in the range of 6–15% with AFM were compared with those obtained with electron backscattered diffraction (EBSD) and light optical microscopy. For TRIP-steels an identification of retained austenite with MFM was found to show a better resolution than classical light optical microscopy.