Grain boundary liquid metal wetting:: A synchrotron micro-radiographic investigation

The penetration of liquid metals into the grain boundaries (GB) of solid metals can lead to severe embrittlement of the solid. Grain boundary wetting, which is the precursor process of liquid metal embrittlement, is still far from being well understood. We report in situ observations of the propagation kinetics of liquid metal into the GB of bicrystals and polycrystals. The experiments are performed using synchrotron radiation micro-radiography. This imaging technique is well adapted for the in situ non-destructive bulk characterization of such phenomenon due to suitable spatial and temporal resolutions. Experiments have shown that the Ga penetration front in aluminum bicrystals propagates roughly with linear time dependence, whereas a discontinuous behaviour occurs in polycrystals. (C) 2002 Elsevier Science B.V. All rights reserved.