Notch Effect on the Tensile Properties of Fast-Reactor-Irradiated Type 304 Stainless Steel

Abstract

The effects of two notch geometries on the tensile properties of fast-neutron-irradiated, annealed Type 304 stainless steel were investigated. Notch strengthening was observed under test conditions that promote transgranular failure accompanied by significant ductility (>5% total elongation) as measured using an unnotched specimen. These conditions existed at room temperature and moderate fluence levels (∼3 to 6 x 10²² n/cm², E >0.1 MeV, ∼3 to 6 x 10²⁶ n/m², E >16 fJ). No notch effect was observed at 450 and 700°F (505 and 644 K) at any fluence level investigated. A notch weakening may exist under test conditions promoting low ductility (<1.5% total elongation) intergranular failure. At a nominal tensile strain rate (2.67 x 10^-3/min, 4.45 x 10 ^-5/s), notch weakening was exhibited near 1100°F (866 K) and neutron fluences above 3 x 10²² n/cm² (3 x 10²⁶ n/m²). At a nominal strain rate, the notch sensitivity is independent of notch geometry between radii of 0.003 and 0.030 in. (0.076 and 0.76 mm). The notch sensitivity becomes notch geometry dependent at higher strain rates due to higher ductilities associated with a transition in the deformation and failure mode.