The study of random alloys is of large interest in metallurgical sciences due to the significant influence of solute solution strengthening on the yield stress. This solid solution strengthening is particularly taken advantage of in the recent development of HEAs. In these alloys, the proximity of atoms of different sizes leads to small displacements of atoms with respect to their lattice sites that are also called micro-distortions. These micro-distortions are accompanied by internal stresses that impede dislocation motion and are responsible for the solid solution strengthening.

To investigate solid solution strengthening in concentrated alloys, our work is articulated around two steps. We first developed an elastic model of random alloys where atoms of different sizes are modeled as Eshelby inclusions embedded in an isotropic elastic medium. This allows to derive analytical expressions for the mean squared displacements and for the mean squared internal stress that impedes dislocation motion. Our elastic model can be used not only to obtain the variance of the displacement and stress fields but also their spatial correlations. Surprisingly, we show that stress correlations are highly anisotropic despite the use of isotropic elasticity and the randomness of the alloy.

The second step consists in using this correlated stress environment in a dislocation dynamics framework to derive the critical stress leading to the dislocation depinning. Adding a Langevin noise also allows us to follow the dynamic of the dislocation with temperature and to investigate how the applied stress influence the energy barrier distribution. These numerical results allow to critically assess the validity and the limitations of average models from the literature.