Fast penetration of liquid gallium in polycrystalline aluminum films

Abstract

From optical microscopic observations a small drop of liquid gallium placed on an aluminum thin film has been found to form arachnoid rises on the film surface. In addition, metallic luster was lost in a bigger region concentrically extending from the position of the gallium drop. These must have occurred because of the penetration of gallium atoms into the film. The speed of gallium webbing was measured to be 2.3 μm/s to 9.1 μm/s, depending on the film thickness, the temperature and the amount of gallium drop. On the other hand, the dull region extended at the speed of approximately 0.83 μm/s, insensitively to the above factors. The embrittlement of aluminum by liquid gallium can be associated with this fast penetration of liquid gallium.