Dislocation Structures Formed inside Dislocation Channels of Rapid-Cooled and Tensile-Deformed Aluminum Single Crystals

Abstract

Dislocation structures inside the cleared dislocation channels in rapid-cooled and tensile-deformed aluminum single crystals were investigated by using transmission electron microscope (TEM). The present study especially focused on the dislocation structures at their early formation stage. In their very beginning stage, arrays of prismatic dislocation loops of the primary slip system were essentially formed elongating along [1 2 1]direction and each prismatic loop stacked to [1 0 1]. With the progress of plastic deformation, the number of the prismatic loops composing the array increased and produced tangled structures with dislocations of the primary coplanar slip system. The tangled structures may act as strong obstacles against the following primary dislocations and become a triggering factor for the creation of the cell structure.

Fig. 10 TEM images of dislocation structures inside a cleared dislocation channel (different channel of Fig. 9) of the primary slip system in a thick area of a foil taken from the specimen elongated to 12.1% macroscopic tensile strain. (a) z ≅ -1 -1 2 and g = 1 1 1, (b) z ≅ 0 1 1 and g = -1 -1 1. In (b), arrows with dotted lines show projected traces of [-1 0 1], [-1 2 -1], [0 1 -1] and [-2 1 -1] on the photo surface. Thicker “band-shaped” weak contrasts “T₁” and “T₂” in (a) were tangled structures “T₁” and “T₂” consisting of arrays of prismatic loops of the primary and the primary coplanar slip systems in (b). In (b), “P” were isolated prismatic loops (primary slip system), “P_B2” isolated prismatic loops (primary coplanar slip system) and “S_B2” screw dislocations with cusps (primary coplanar slip system). “Band-shaped” weak contrasts “D” in (a) were considered to be arrays of prismatic loops of the primary slip system.