The fracture toughness behaviour of austenitic steels and weld metal including the effects of thermal ageing and irradiation

Tritium Aging Effects on the Fracture Toughness Properties of Forged Stainless Steel

“…That fact that sensitization occurs in high-energy-rate forgings has been pointed out in earlier studies (12)(13)(14) and it may appear occasionally in reservoir microstructures. Furthermore, since cold work and nitrogen increase the kinetics of sensitization in Types 304L and 304LN stainless steels (15)(16), these factors will increase the potential for sensitization in Type 21-6-9 stainless steel, too. The reservoir manufacturing community should be diligent in ensuring that any potential for sensitization be minimized because of its detrimental effect on fracture toughness.…”

“…A variety of substructures can evolve from the forging process (1, 15) because of either dynamic or static recrystallization. Static recrystallization, which can go to completion within a few seconds after cessation of deformation, is the dominant restoration mechanism in high-energy-rate-forged material (15). High densities of dislocations appear to limit the quantity of helium that can accumulate at a grain boundary, where it forms pressurized bubbles and clusters that will cause an additional stress on the boundary, and reduce the cohesive area (1).…”

Crack growth rates and fracture toughness of irradiated austenitic stainless steels in BWR environments.

“…For fluences less than 5 dpa, as shown in Fig. 75, the existing fracture toughness data can be bounded by a power-law J-R curve with coefficient C expressed as C = 20 + 205 exp(-0.65 dpa), (26) and an exponent n equal to 0.37 (the median value of the experimental data). This equation yields a bounding C value of !…”

“…[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In these studies, the embrittlement of the materials has been characterized in terms of tensile properties, Charpy-impact properties, and fracture toughness. Irradiation damage is characterized by either the neutron fluence in neutrons per square centimeter (n/cm 2 ) or the average number of displacements experienced by each atom, i.e., displacements per atom (dpa).…”

“…1a and b, respectively. 2,3,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] The fast reactor data show a rapid decrease in fracture toughness at a neutron dose of 1-2 dpa (Fig. 1a); the neutron dose at the onset of the rapid decrease varies with the chemical composition and heat treatment of the steel.…”