Interface morphologies and embrittlement behavior of α-Fe in liquid lead-bismuth eutectic at elevated temperature

The grain-boundary penetration behavior and interfacial characteristics of α-Fe in lead-bismuth eutectic (LBE) at 900 °C have been investigated. The results indicate that α-Fe can be completely embrittled by liquid LBE in forms of grain boundary (GB) grooving by liquid Bi and Pb segregation at GBs. Deep GB grooves and long-narrow LBE penetrated film occur at low dihedral angle of α grains along triple junctions; while discontinuous LBE particles with 1 μm in diameter can spread at GBs of high dihedral angle or distribute within α grain interior. The discontinuous LBE particles can further aggregate and transfer into grain-boundary films to cleave α grains from substrate. GB morphology strongly dominates liquid LBE grooving and penetration depth, depending on the original GB dihedral angle. Obvious microcracks and dynamic dihedral angle ahead of GB root determine the LBE penetration direction and subsequent grooving, probably depending on the grain orientation and energies. Meanwhile, the interfacial Fe-atom removal/redeposition and strong segregated Pb/Bi atom multilayer absorption may govern solid/liquid interfacial grooving, diffusion and penetration of LBE film via solid/liquid bridge-joint interface atom transfer mechanism.