Influence of liquid lead and lead-bismuth eutectic on three alumina forming austenitic (AFA) steels through slow strain rate testing

Abstract

Liquid metal embrittlement (LME) in three newly developed alumina-forming austenitic (AFA) alloys, two 50 kg batches and one 5-ton heat, was studied in the temperature range 350–600 °C in liquid Pb and 140–600 °C in LBE using slow strain rate testing (SSRT) in a low-oxygen environment. No significant decrease in the engineering strain was observed in either environment. However, the presence of secondary cracks along the length of the specimen and brittle intergranular areas on the fracture surfaces indicates that the AFA alloys do show a minor degree of embrittlement above 570 °C. This appears to be related to grain boundary wetting by Pb/LBE. At temperatures below 570 °C, this wetting effect does not seem to be strong enough to induce LME in the alloys, and their ability to form a sufficiently protective oxide means that they remain unaffected by LME. The results indicate that the AFA alloy group can perform sufficiently well in liquid Pb/LBE environments, and long-term testing should be carried out to determine their viability as candidate materials for use in Pb- and LBE-based cooling systems.