Abstract FR:

In a large number of metallic and ceramic systems, rapid penetration (10-3-100 mm/s) of microscopic intergranular liquid films along grain boundaries of the host material occurs and can provoke its mechanical decohesion. Because brittle fracture in any structural material involves human tragedy, a better understanding of the mechanisms behind it is of highest interest. Grain Boundary Penetration (GBP) of liquid Ga in Al grain boundaries has been investigated via Synchrotron Radiation X-ray Imaging. While for Al bicrystals the Ga layer propagation is linear and thickens in continuous manner, a discontinuous behaviour is found in polycrystals. In both cases, the kinetics is strongly influenced by stress. GBP in Al/Ga seems to be an "invasion-like" process where the intruding liquid separates the grains when penetrating.