VOID DAMAGE IN NEUTRON IRRADIATED STRUCTURAL METALS
0 The tensile and creep-rupture properties of types 304 and 304-+ 0.15$ Ti stainless steels have been determined after irradiation at temperatures in the range 370-800°C to maximum fast neutron fluences of 3 x 10 22 neutrons/cm 2 (> 0.1 MsV). Changes in mechanical properties were related to the irradiation produced defects. When irradiated in the annealed condition in the neighborhood of 40Q°C, type 304 stainless steel exhibited an increased yield stress, reduced strain hardening coefficient
... ning coefficient and reduced uniform and total elongation. The increased yield stress could be correlated vith the strengthening expected from irradiation produced voids and dislocations. With increasing irradiation temperature the concentration of these defects decreased and thus the magnitude of the yield stress increase became less. At 500 to about 600°C a pronounced reduction in creep-rapture ductility was observed. Fractures vere intergranular. It is suggested that in this temperature range the void-dislocation structure together vith the transnutation produced helium vere responsible for the intergranular fractures and low ductilities. At higher temperatures no void-dislocation structures vere formed. For these conditions the ductilities vere higher than in the 500-600'C range but still significantly below the unirradiated value. Variation in alloy composition and preirradiation microstructure had a strong influence on the postirradiation properties. Type 304 + 0.15$ Ti exhibited significantly higher tensile and creep-rupture ductilities than the. standard alloy when irradiated and tested at 450°C and above. "Research sponsored by the U.St Atomic Energy Commission tinder contract I / vith the Union Carbide Corporation.