Microstructural changes of T-91 alloy irradiated by Fe self ions to ultrahigh displacement ratios

Modified 9Cr-1Mo steel T91, a candidate material for structural components in fission reactors, was irradiated with 3.5 MeV Fe ions at 450 °C to 150 displacements per atom. Transmission electron microscopy and scanning transmission electron microscopy were used to characterize the microstructure and microchemistry changes. We found that irradiation can induce formation of needle-like M3C particles, in addition to voids and tangled dislocations. But for these preexisting precipitates their compositions remain roughly the same before and after the irradiation. Furthermore, we did not observe either Cr depletion or Cr enrichment at grain and subgrain boundaries after the irradiation.