Enhanced toughness and ductility of T91 steel after exposure to liquid LBE saturated by oxygen at 350–500 °C

The mechanical tensile properties of T91 steel after being oxidized in liquid LBE saturated by oxygen at 350–500 °C for up to 1000 h are studied. Duplex oxide scales are found on T91 steels after the LBE exposure, and the thickness evolution is revealed. Oxidized T91 steels with surface oxide scale yield enhanced toughness and ductility, which is mainly attributed to the inner oxide layer. We show that the enhancing effect relies on the presence of the oxide scale, not its thickness. The possible enhancing effect of the oxide scale on the toughness of T91 steel by impeding the dislocation from emitting out of the steel surfaces is discussed and qualitatively verified by micro-scale elastoplastic simulations based on a newly proposed discrete dislocation dynamics and peridynamics superposition scheme. •The oxide scale thickness evolution of T91 steel in oxygen-saturated LBE at 350–500 °C is revealed.•T91 steel after being oxidized in liquid LBE yields enhanced toughness and ductility.•The enhancing effect relies on the presence of the oxide scale, not its thickness.•Oxide scale might serve as an obstacle to dislocation slips in the materials during plastic deformation.•The possible mechanism is analyzed by micro-scale elastoplastic simulations.