Strange behavior of dislocations of a certain type: Self-locking

Resumo

The results of studying the self-locking of dislocations, namely, the transformation of glissile dislocations into blocked dislocations in the absence of an applied stress, are generalized. The existence of selflocking is theoretically grounded and experimentally proved via the observation of dislocation extension along a preferred direction upon loading-free heating after preliminary plastic deformation. The following concept is developed to explain the experimental results: an effective force appears in the case of a two-valley dislocation potential relief; it is proportional to the difference between the valley depths and causes the transformation of a dislocation into an indestructible barrier. The temperature anomaly of yield strength and the dislocation self-locking are shown to have the same nature—a two-valley dislocation potential relief. Both effects were observed in Ni₃Al- and TiAl-type intermetallics and a pure metal (magnesium).