The dependence of discontinuous deformation on orientation in AlMg single crystals

Abstract

The effect of crystal orientation on the discontinuous deformation in Al-0.3wt.%Mg single crystals was investigated at room temperature. The magnitude of the serrations increases with increasing strain up to the end of stage II and then gradually decreases in all specimens. It becomes roughly constant in stage III. Serrations with a sharp large amplitude were observed in the deformation of [111] single crystals and these correspond to the occurrence of a large local strain which abruptly appears and increases in a step-by-step manner. In contrast, broad serrations with a small amplitude were observed in the deformation of specimens which belong to single- and double-slip systems. Moreover the local strain increases gradually with increasing strain in both specimens. A Lüders band of conjugate slip was observed at stage III for the specimen of the double-slip system. On the basis of these results, we conclude that the discontinuous deformation in an AlMg single crystal is closely related to the heterogeneous deformation of the specimen so that the shape and magnitude of the serrations are strongly affected by the distribution and nature of obstacles which are formed by interaction between dislocations.