Abstract：The recent use of the Focused Ion Beam (FIB) microscopes has allowed fast developments in materials science. The interest from the steel industry for the FIB technique is not only related to the ever decreasing thickness of coatings and passivation layers. Indeed, the FIB technique is particularly adapted for the preparation of TEM lamellae of multiphase or very heterogeneous and/or porous materials. Four years ago, a triple beam FIB instrument was installed at ArcelorMittal Gent and since then, a wide variety of materials have been screened and/or processed for further TEM analysis. FIB was successfully applied in the field of coating, substrate and interface studies e.g.1) Coating applications: thickness-homogeneity, defectology, corrosion studies; 2) Substrate analysis: crack propagation, grain boundaries, grain orientations;3) Interface analysis: intermetallic phases, diffusion and segregation, epitaxial studies. The high cost of a FIB instrument and the dedicated operator skills are certainly drawbacks for its routine applications in steel research. Nevertheless, a lot of economical benefit can be gained from the its unique way of sample preparation such as the shorter sample preparation time, the choice or selectivity of the sampling area, and of course, the extremely limited effect of artefacts. Very often, FIB sample preparation is the only way to produce TEM lamellae that cannot be obtained by other preparation techniques. FIB in combination with TEM analysis opens a new world of chemical, microstructural and crystallographic information as will be highlighted in the following topics.1)Eutectic phase characterization of Zn-Al-Mg coatings; 2)Defectology studies of Cr-rich passivation layers; 3)Structural composition of weathering steels; 4)Microctructure of Zn-free coatings: Aluminium/Magnesium showing nano crystalline Al-Mg rich phases.
