CHARACTERIZATION OF 25-75 NM PHASES FOUND AT THE PERIPHERY OF MULTIPHASE INCLUSIONS - TECHNIQUES COMPARISON AND SELECTION

It is believed that particular phases found at the surface of inclusio ns in steel welds favour the formation of acicular ferrite. Such a mic rostructure increases tremendously the toughness of the weld deposits, Until now, it is not clear which phases are favourable, the uncertain ty being partly due to the difficulty of characterizing phases with si zes of about 100 nm at the periphery of inclusions. We compared charac terization techniques including scanning electron microscopy, transmis sion electron microscopy energy-dispersive spectrometry and parallel e lectron energy-loss spectroscopy We found that, in general, it is poss ible to identify the phases unambiguously by comparing the results of energy-dispersive spectrometry and electron diffraction patterns in th e transmission electron microscope on samples prepared by carbon extra ction replicas, For cases where the size is very small (< 50 nm) and/o r when similarities in composition and crystal structure are difficult to differentiate, spectrum imaging using parallel electron energy-los s spectroscopy on samples prepared by ultramicrotomy is the most power ful characterization technique.