Structural and chemical matrix evolution following neutron irradiation in a MA957 oxide dispersion strengthened material

The MA957 alloy has been irradiated in the french Phenix reactor at 412 °C up to 50 dpa and at 430 °C up to 75 dpa. For both irradiation conditions, the evolution of the matrix after neutron irradiation has been investigated by transmission electron microscopy especially focusing on the creation of structural defect as the dislocation loops and on the chemical evolution of the matrix. Some loops have been investigated and are found to be 〈100〉{1 0 0} interstitial type loops. Further, it is shown that the largest Ti-rich particles start to dissolve and release in the surrounding matrix their component elements. Those elements could segregate to the grain boundary. Both irradiation conditions systematically lead to the formation of α′ nano-cluster and Cr depletion at grain boundary.