Microstructure and mechanical properties of α-particle irradiated stainless steels

Abstract

The effect of helium injected in stainless steels on the mechanical properties are investigated. The materials used are 100 μm thick foils of type 316 austenitic stainless steel, dual phase (9Cr-2Mo, ferritic and martensitic phase) stainless steel and duplex (22Cr-5Ni, ferritic and austenitic phase) stainless steel. The tensile strength (0.2% proof strength and ultimate strength in room temperature tensile test) of these materials increased slightly with the amount of injected alpha particles, but the elongation of these steels decreased with the alpha particle dose. Intergranular type fracture was observed only on the 316 stainless steel in which alpha particles had been injected in amounts up to 1.3 × 10 17 cm −2 at the depth of range. Transgranular fracture occurred on a post-injection annealed 316 stainless steel and on the other materials. The transmission electron microscope observation of helium bubble distribution established that the intergranular fracture is caused by a highly dense distribution of small helium bubbles at grain boundaries.