Self-blocking of dislocations: A new concept

Abstract

The effect of self-blocking (transformation of dislocations at zero external stress from sliding configurations into blocked ones) was theoretically predicted and then found in Ni3(Al, Nb) and TiAl alloys. The physical reasons for self-blocking are revealed. The thermally activated dislocation flip from a shallow potential relief valley into a deep one is shown to be the controlling process. It occurs through the formation of a double kink with its subsequent reorientation, leading to the formation of an asymmetric kink and the extension of dislocation along the preferred direction. The driving force of this process is calculated and its conditions are formulated. It is shown on the basis of a set of experimental data that the multivalley character of the potential relief plays a key role in the dislocation blocking and self-blocking. It is proven that both effects—the yield stress anomaly and self-blocking—have the same nature: a two-valley potential relief of dislocation.