Investigation of precipitation hardening by dislocation dynamics simulations

Dislocation dynamics (DD) simulations are used to investigate precipitation-induced strengthening in a Zr-1 % Nb alloy. A method is proposed to carry out simulations under dynamical conditions in connection with the microstructure of the investigated alloy. First, a sensitivity study of simulation parameters, suspected of altering simulation results, is presented. It allows setting up simulation conditions ensuring statistical representativeness. The effect of the strain rate is then investigated and analyzed in connection with the random distribution adopted to describe precipitation distribution. The strengthening induced by two different families of Nb precipitates is estimated from simulations whose simulation box is reduced to the volume of a single grain. It is shown that the obtained strengthening values are smaller than those predicted by most published models. Determination of total strengthening shows that usual superposition rules do not apply. A mixture law, fitting DD results well, is proposed in this paper.