Microstructure evolution of two model ferritic/martensitic steels under in situ ion irradiation at low doses (0–2 dpa)

Ferritic/martensitic steels are candidate materials for structural and cladding components designed for Generation IV reactors because of their superior resistance to radiation damage at the high operating temperatures envisioned in these reactors. To enable the development and optimization of such advanced alloys for in-reactor use, a fundamental understanding of radiation damage accumulation in materials is required. In this work, two model F/M steels (12Cr model alloy and 9Cr model alloy) were irradiated with 1 MeV Kr ions at 50 K, 180 K, 298 K, 473 K and 573 K in situ in a TEM. The microstructure evolution under irradiation was followed and characterized at successive doses in terms of irradiation-induced defect formation and evolution, defect density, size distribution and interaction with the as-fabricated microstructure (e.g. dislocation networks, lath boundaries) using weak-beam dark-field imaging. The effect of the irradiation temperature on the defect kinetics is assessed at doses up to 2 dpa.