Kinetics of penetration of the bismuth melt along the grain boundaries of copper

Abstract

Kinetics of developing the channels of through penetration of the bismuth melt along the grain boundaries (GBs) and triple joints (TJs) of grains in thin (from 120 to 500 μm) polycrystalline samples of copper is investigated by direct visual observation in situ using a LEICA-L2 optical microscope. For experiments, as a source of metal materials have been used copper with a purity of 99.995 wt % and bismuth—99.999 wt %. Copper samples had an average grain size of 30–50 μm. When investigating them after holding them in contact with the bismuth melt at temperatures from 490 to 600°C, microscopic photographs which indicate the penetration of Bi through Cu wafers, as well as the image of the network of liquid-metal channels in transverse sections of the samples, were obtained. The temperature dependence of the penetration rate of the melt through the wafers of polycrystalline copper and the effective activation energy of penetration of Bi along the GBs are found.