Helium entrapment in a nanostructured ferritic alloy

Microstructure of HIPed and SPSed 9Cr-ODS steel and its effect on helium bubble formation

“…Our results show that helium bubbles formed in 14Cr-ODS steel exhibited smaller size and lower volume fraction than in Eurofer 97 steel [14]. Analyses conducted by transmission electron microscope (TEM) and atom probe tomography (APT) have indicated that dislocations, grain boundaries and the surface of precipitates were the preferential trap sites for absorbing helium atoms [5,6,15]. Similarly to the nano-oxides in ODS steel, grain and phase boundaries can also effectively absorb the radiation-induced defects and trap helium atoms as revealed in nanocrystalline metals and multilayers [16e18].…”

“…Helium bubbles are easily trapped at the microstructure defects, such as dislocations, grain boundaries and the surface of precipitates. Helium accumulation under high stress at elevated temperatures may cause formation and growth of voids and grain boundary creep cavities, resulting in degradation of fatigue, thermal creep, creep rupture and creep fatigue properties, especially the tensile ductility due to helium embrittlement [5,6].…”

Small-scale characterisation of irradiated nuclear materials: Part I – Microstructure

“…system through inhibiting dislocation motion and grain boundary sliding. In nuclear applications the oxide particles have been suggested to act as point defect sinks [10,11] to improve radiation tolerance, and as preferential sites for the formation of nano-scale He bubbles therefore reducing swelling compared to non-ODS steels [12][13][14][15]. The ability of the oxide particles to improve these properties depends on the structure and composition of the particles [10,11,16,17] and their stability under irradiation.…”

A review of advantages of high-efficiency X-ray spectrum imaging for analysis of nanostructured ferritic alloys

“…In addition, finer Ti 2 Y 2 O 7 precipitates and Ti-Y-O-enriched nanoclusters (NCs) are present both within the matrix grains and along the grain boundaries [7,[15][16][17][18]. Helium irradiations indicate significant sequestration of bubbles at the NCs [19][20][21][22].This combination of a complex, multi-length-scale microstructure with important engineering applications makes NFAs (specifically 14YWT) a materials system that would benefit from new structural analysis methodologies.…”