The first observation of dislocation blocking in pure metal without external stress

摘要

Self-blocking of c + a edge dislocations at second-order pyramidal slip in magnesium single crystals whose axis is parallel to the c axis has been found. Self-blocking is confirmed by the dislocation extension along a selected direction in the absence of external stress. Transmission electron microscopy (TEM) images of (c + a) dislocations extended in the <1 100> directions are obtained. A model of a two-valley potential relief in Mg is proposed: the Peierls relief determines the second-order slip of (c + a) dislocation in the pyramid plane, while the immersion in deep valleys is related to splitting of the c + a edge segment (or the spread of its core) in the basal plane.