  We use a discrete dislocation dynamics (DDD) approach to study the motion of
a dislocation under strong stochastic forces that may cause bending and
roughening of the dislocation line on scales that are comparable to the
dislocation core radius. In such situations, which may be relevant in high
entropy alloys (HEA) exhibiting strong atomic scale disorder, standard scaling
arguments based upon a line tension approximation may be no longer adequate and
corrections to scaling need to be considered. We first study the wandering of
the dislocation under thermal Langevin forces. This leads to a linear
stochastic differential equation which can be exactly solved. From the Fourier
modes of the thermalized dislocation line we can directly deduce the scale
dependent effective line tension. We then use this information to investigate
the wandering of a dislocation in a crystal with spatial, time-independent
('quenched') disorder. We establish the pinning length and show how this length
can be used as a predictor of the flow stress. Implications for the
determination of flow stresses in HEA from molecular dynamics simulations are
discussed.

Materials Science