SMALL-ANGLE GRAIN-BOUNDARIES AS LATTICE DISLOCATION SOURCES NEAR THE MELTING-POINT OF ALUMINUM

Direct observations of the melt growth process of aluminium crystals have been made using synchrotron white beam X-ray topography. It is shown that static small angle grain boundaries can act as sources of lattice dislocations when they are forming from melt. The lattice dislocations are nucleated from the point of emergence of the small angle grain boundaries at the solid-liquid interface and from steps or ledges in the grain boundaries by the relaxation of stresses concentrated either in the solid-liquid interfacial area or along the grain boundary steps. © 1990.