Representation of Elevated-Temperature Tensile Behavior of Type 304 Stainless Steel in a Sodium Environment

An analysis of tensile behavior of Type 304 stainless steel was conducted for specimens in the solution-annealed condition and after exposure to a sodium environment. The Voce equation was used to describe tensile flow curves for plastic strains above 0.005 at temperatures between 550 and 700°C and strain rates of 3.81 × 10⁻⁶ to 1.90 × 10⁻³ s⁻¹. The results show that, when compared with solution-annealed specimens, the tensile flow behavior of the sodium-exposed specimens is characterized by a higher strain-hardening rate, which decreases rapidly with an increase in flow stress. The values of the saturation stress for uniform elongation predicted from the Voce model are higher for the sodium-exposed specimens than for those in the solution-annealed condition at strain rates ≲5 × 10⁻⁵ s⁻¹ and lower for strain rates ≳5 × 10⁻⁵ s⁻¹. Metallographic examination of the fracture surfaces shows a transition from a complete ductile fracture to a partial intergranular failure as the strain rate decreases. Carburization of the specimens appears to inhibit the intergranular failure.