Study of Microscopic Origins of Radiation Hardening of Eurofer 97 in Simulation Experiment with Ion Irradiation

Low-temperature radiation hardening of prospective structural steel Eurofer 97 as the material for the first wall of the DEMO fusion reactor is studied in this work. Specimens of Eurofer 97 steel were irradiated with Fe ions up to 10 dpa at temperatures of 250, 300 and 400°C. Irradiated samples were studied by transmission electron microscopy and atom probe tomography. TEM study of irradiated samples showed preferential formation of dislocation loops at all temperatures of irradiation. Pair-correlation function analysis detected the initial stage of matrix solid solution decomposition of Eurofer 97 steel only at the temperature of 400°C. Detected microscopic changes and calculated hardening in the framework of the DBH (dispersed barrier hardening) model have shown that formation of dislocation loops is the main origin of low temperature radiation hardening of Eurofer 97 under irradiation with Fe ions with fluence up to 10 dpa.