Deformation and cracking of irradiated austenitic stainless steels

Samples of proton-irradiated 304L stainless steel were deformed by constant extension rate tensile tests at strain rates of 3 {times} 10{sup {minus}7} s{sup {minus}1} and 3 {times} 10{sup {minus}8} s{sup {minus}1} to strains of up to 10% at 288--350 C in argon. Minor cracking was observed in and around spinel inclusions in the material, however no intergranular cracking of the type observed in water environments was found. Thus intergranular cracking cannot occur by a radiation hardening mechanism alone. The microstructures that resulted from irradiation and deformation were characterized using electron microscopy. Surface slip band formation is observed on one or two {l_brace}111{r_brace} slip systems in each grain. The slip bands correspond to dislocation channels in the material as identified by transmission electron microscopy. The channels form by activation of grain-boundary dislocation sources, with the emitted dislocations sweeping through the grain interior to the opposing rain boundaries. During this process, the dislocations remove the radiation-produced defects. Slip band and dislocation channel densities increase with increasing strain in the samples. These results are used to interpret stress corrosion cracking behavior in this material.