Mechanical properties and microstructure of a FeCrAl-ODS alloy under long-term thermal aging at 700 ℃ up to 10000 h

Abstract

Long-term aging effects were studied on the FeCrAl-ODS alloy at 700 °C up to 10000 h to reveal changes in mechanical properties and microstructures. The microstructure of the alloy before aging consists of fine and elongated grains, and high density of dislocations and nanoparticles. The nanoparticles have an average diameter of approximately 9 nm and a number density of 1.3 × 10²³ m^-3, identified as orthorhombic YAlO₃ and Y₂(Zr_0.6Ti_0.4)₂O₇ coherent with matrix. After aging at 700 °C to 10000 h, the reduction of hardness and tensile properties at both room temperature and 700 ℃ were negligible. The total elongation tested at 700 °C was about 49%, which was significantly higher than most of the ODS alloys in the literature and very beneficial for the fabrication of cladding tubes. The fracture modes of the tensile specimens remain unchanged by aging. No noticeable recovery of grain/sub-grain structures or dislocations occurs during aging. The uniform distribution, average size, number density and coherence with the matrix of nanoparticles remain almost unchanged by aging. The FeCrAl-ODS alloy exhibits superior thermal aging stability in terms of the microstructure and mechanical properties during long-term thermal aging treatment at 700 °C, which is promising for application in advanced nuclear energy systems.