Atomistic simulation of precipitation hardening in α-iron: influence of precipitate shape and chemical composition.

Classical molecular dynamics simulations of the interaction of edge dislocations with precipitates in α-iron are performed. The critical resolved shear stress (CRSS) is determined for various morphologies of precipitates: pure copper and nickel precipitates, ordered and unordered copper/nickel precipitates, copper and nickel precipitates with substitutional iron atoms, copper precipitates of ellipsoidal shape, and copper precipitates with nickel shells. The dependence of the CRSS on the nature of the precipitate is explained by considering the Burgers vector distribution within the precipitates. It is shown that, except for the ordered precipitates, chemical inhomogeneities of the precipitates lower the CRSS with respect to the precipitates consisting of the pure phases. [ABSTRACT FROM AUTHOR]