Phase stability in proton and heavy ion irradiated ferritic–martensitic alloys

Phase stability of precipitates in ferritic–martensitic alloys T91, HCM12A, HT-9 and a 9Cr model alloy following proton irradiations up to 10 dpa at 400 °C and 500 °C and heavy ion irradiation to 100 dpa at 500 °C were examined using transmission electron microscopy and atom probe tomography. Both the average size and the Cr/Fe ratio of the grain boundary carbides were altered by irradiation in T91. Ni/Si/Mn-rich, Cu-rich and Cr-rich precipitates formed in alloys T91, HCM12A and HT-9 under certain irradiation conditions. Irradiation at 500 °C produced substantially larger Ni/Si/Mn-rich and Cu-rich precipitates but at much lower number density compared to irradiation at 400 °C. Cr-rich precipitates were observed in HCM12A and HT-9 with higher bulk Cr content than the solubility limit of Cr at the irradiation temperature. Heavy ion irradiation produced precipitates of similar size and composition to those induced by proton irradiation at the same temperature but at a lower number density.