Stress–strain curves of a T91 f/m steel tested in tension in Ar+5%H₂ and oxygen-poor (C _O ≈ 10⁻⁹–10⁻¹⁰ mass%) static liquid LBE. Both tests were conducted at 350 °C under an applied strain rate of 5 × 10⁻⁵ s⁻¹. The specimen tested in LBE was pre-exposed at 450 °C in low-oxygen liquid LBE. The fracture surface of the specimen tested in LBE (A) shows areas that suffered quasi-cleavage (B) failure. Also, the inspection of the specimen necking region shows the formation of numerous side cracks (C).