The tensile properties of the columbium-stabilized austenitic steel FV548 have been investigated after irradiation in a thermal reactor up to fluences of 4 · 10²⁰ n/cm² (thermal) and in a fast reactor up to fluences of 2.7 · 10²² n/cm² (total).

The parameters that have been studied include the effects of irradiation temperature, covering the temperature range 550 to 750 C (1022 to 1382 F); the effects of solute level produced by increasing the solution heat-treatment temperature from 950 to 1300 C (1742 to 2372 F); and the effects of pre- and postirradiation aging. Testing has been carried out over the strain-rate range 5 · 10⁻⁴ to 5 · 10⁻⁶ per second and at temperatures between 550 and 750 C (1022 and 1382 F). The microstructures obtained during irradiation have also been investigated and the results correlated with the tensile properties. Suggested mechanisms for the effects observed are discussed.