Abstract
Sub-boundaries in Al single crystals grown from the melt under various conditions were studied by means of X-ray Laue diffraction, pseudo-Kossel lines, transmission electron microscopy and selected area electron diffraction.
The results obtained are as follows:
(1) Besides sub-boundaries comprised of a regular array of dislocations or dislocation networks, a new type of sub-boundaries composed of fine tangling dislocation segments was frequently observed.
(2) The new type sub-boundaries lay in the {311} or {211} planes.
(3) Relations between the structure of the sub-boundaries and the misfit angle across the boundaries, the growth rate and the purity of the crystals were examined.
(4) Experiments to determine the Burgers vectors of the tangling dislocation segments suggested that strains around them may be described by assuming a certain vector which is the vector sum of the Burgers vectors of the segments.
(5) The interactions of edge dislocations arising from collapsed vacancy disks, screw dislocations which are moving actively in the crystal after the solidification, and impurities seem to strongly influence the formation of the sub-boundaries, leading to the appearance of a complicated structure of the sub-boundaries.
