Microstructure and mechanical properties of two ODS ferritic/martensitic steels

A microstructural analysis and tensile tests were performed on two oxide dispersion strengthened ferritic/martensitic steels. Dispersion hardening represents an interesting approach to improve the mechanical properties at elevated temperatures, as they are foreseen in the future fusion reactor, while maintaining the inherent advantages of the ferritic/martensitic steel in an irradiation environment (high thermal conductivity and low swelling rate). The base material is the ferritic/martensitic steel EUROFER 97 with the chemical composition Fe, 8.9 wt% Cr, 1.1 wt% W, 0.47 wt% Mn, 0.2 wt% V, 0.14 wt% Ta and 0.11 wt% C. In one steel the strengthening material Y ₂O ₃ represents 0.3 wt% while in the second it represents 0.5 wt%. It appears that the ODS with 0.3 wt% yttria presents, in terms of critical stress and uniform elongation, a better mechanical behaviour than the base material up to 500 °C and still maintains fair properties up to 700 °C.