Effects of the stacking fault energy fluctuations on the strengthening of alloys

Abstract In alloys and high entropy alloys the stacking fault energy varies with the local composition. The effects of these energy fluctuations on the strengthening are studied using dislocation dynamics simulations that track the evolution of partial dislocations in FCC metals at zero temperature. Different values of the intrinsic stacking fault energy are assigned to regions with size in the range of 0.5 nm–12 nm in the slip plane, while the other mechanical properties are left constant. A theoretical model is derived and compared to the simulation results. In the model and the simulations the predicted value of the yield stress grows with larger fluctuations of the stacking fault energy. Furthermore, a strong size dependency is observed, with a maximum in the strength attained when the mean region size approaches the average equilibrium stacking fault width. In summary, the strength of high entropy alloys can be improved by introducing disorder in the chemical misfit with a characteristic length scale of the order of the average stacking fault width.