YAMADA Katsumi SATO Kaoru NAKAMICHI Haruo
In light of its superior performance in microanalysis, field emission-transmission electron microscopy (FETEM) is a useful experimental apparatus to study advanced steels. After a briefly reviewing the recent progress in TEM and its functions for elemental analysis, the authors used FE-TEM for the analysis of a hot-rolled steel with a tensile strength of 780 MPa. According to the results of the authors, the fine precipitates of an MC type (composition: (Ti0.54Mo0.46)C) was effective in improving the strength of the ferrite matrix. This precipitation strengthening was estimated to be around 250 MPa, based on an analysis of the density of these precipitates. Next, we conducted an EF-TEM experiment on a series of heat-resistant steels that had been strengthened by MX. Fine (V, Cr)N was found to be dispersed in a tempered martensitic steel with superior creep properties. The spatial resolution in elemental mapping of EF-TEM was close to 3 nm in this case.