Slow Strain Rate Testing of advanced metal alloys in liquid lead doped with tellurium

Sammanfattning

As the development of Generation IV lead-cooled fast reactors (LFRs) progresses,ensuring the mechanical integrity of structural materials in harsh core environmentsis essential, especially under accident scenarios involving fission product release.One such concern is Liquid Metal Embrittlement (LME), a phenomenon wherea liquid metal causes a transition from ductile to brittle behavior in structuralalloys. This thesis examines the susceptibility of the ferritic alumina-forming alloyFe10Cr4Al (10-4) to LME when exposed to molten lead contaminated with tellurium(Te), a fission product of particular relevance. Slow Strain Rate Testing (SSRT) isconducted on 10-4 specimens across a range of temperatures, strain rates, and Teconcentrations, using both unnotched and notched samples. For reference, 316Lstainless steel is tested under similar conditions. Topographic and chemical analysis(SEM/EDS) on 10-4 specimens show that LME is most evident in notched samples,where stress concentration damages the oxide layer that forms on the steel surface,promoting liquid-solid contact. The strongest embrittlement occurs at intermediateTe concentrations ( 0.3 wt%), where brittle fracture features dominate. Ductility fullyrecovers at the highest Te content (1.2 wt%), due to the supersaturated solution thatleads to the formation of Te-rich precipitates that limit wetting or reduce effectivephase interaction. Moreover, LME effects are not observed in unnotched specimens atlower strain rates, suggesting that slower deformation helps preserve oxide integrityand enables the formation of protective precipitates that hinder penetration.