Combinig complementary techniques to study precipitates in steels


Understanding the precipitation reactions is of vital importance for the development of advanced steels. A comprehensive characterization of all phases, however, is still demanding in these complex materials. Transmission electron microscopy is widely used, but the prevailing ferromagnetism makes the analysis of small precipitates difficult. Furthermore, the investigated specimen volume is small, making statistically relevant findings time-consuming. Therefore, in our study, transmission electron microscopy measurements are complemented by small-angle neutron scattering and atom-probe field ion microscopy. These methods were used to characterize the precipitates in a model steel which hardens by secondary hardening carbides and an intermetallic NiAl-based phase. Assets and drawbacks of each method are discussed and it will be shown that an appropriate combination of the differently obtained findings leads to a detailed description of the precipitation behavior.
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