Investigation of the relationship between mechanical properties and microstructure in a Fe-9%Cr ODS steel

International audienceFerritic-martensitic Oxide Dispersion Strengthened (ODS) steels are potentialmaterials for fuel pin cladding in Sodium Fast Reactor (SFR) and their optimization is essentialfor future industrial applications. In this paper, a feasibility study concerning the obtaining ofspecimens into a quenched-dilatometer is presented. The ODS steel investigated contains 9%Crand exhibits a phase transformation between ferrite and austenite around 880°C. The purpose wasthe generation of model microstructures and the evaluation of their tensile properties. Thespecimens were machined from a cladding tube and underwent highly controlled heat treatmentsinto the dilatometer. Then, tensile tests were performed on the model microstructures. Thereafter,macroscopic residual stresses relaxation during the heat treatment was evaluated.Results show that a martensitic structure seems to be the most optimized state for the tensileproperties even if a reasonable fraction of ferrite does not appear to be compromising. Moreover,macroscopic residual stresses within the tube linearly decrease upon increasing temperature. Thedilatometer has turned out to be an efficient method to perform analytic treatments and generatemicrostructures. However, in this investigation, experimental phenomena such as decarburizationremain an important source of limitation and need to be controlled