Corrosion mechanism of lead-bismuth eutectic at grain boundary in ferritic steels and the effect of alloying elements: A first-principles study

In this study first-principles calculations are used to investigate the corrosion mechanism of liquid metal embrittlement (LME) by lead-bismuth eutectic (LBE) at grain boundary (GB) in ferritic steels using BCC Fe Σ5 (013) GB. The effects of two important alloying elements (Nb and V) on the LBE corrosion are also considered. Our results show that Pb and Bi are prone to permeation along the GB. Pb and Bi in Fe GB will induce GB expansion and form weak bonds, and thus weaken the GB cohesion, inducing a significant decrease in work of separation and maximum GB strength. Our studies also show that the LME sensitivity of Bi is greater than that of Pb, which is consistent with the experimental results. Furthermore, Nb and V are found to have a hindering effect on the crack generation caused by Pb and Bi, and can somehow improve the ability against the LBE corrosion. Our theoretical study provides a fundamental understanding of LBE corrosion mechanism in ferritic steels and can serve as the foundation for improving ferritic steels through alloying elements.