Detection of (C + A)-type dislocation self-blocking in magnesium

The self-blocking effect predicted theoretically and then observed in intermetallides is established for a pure metal, namely, for magnesium. This effect can be observed only for magnesium single crystals whose axis is parallel to the c axis and whose yield stress behavior σ y ( T ) has a temperature anomaly. For such single crystals, the self-blocking of the ( c + a )-type edge dislocations is established during pyramidal slip of type II. The self-blocking is proved by dislocation extension along the preferred direction without external stress. In this case, the directions appear preferred. TEM images of ( c + a ) dislocations extended along the preferred directions are presented. It is demonstrated that two effects – temperature anomaly of σ y ( T ) and dislocation self-blocking – have the common nature: a two-valley potential relief of the dislocation. A model of two-valley relief of the ( c + a ) dislocations in Mg is proposed.