Interaction between prismatic slip and a Mg17Al12 precipitate in magnesium

Interaction mechanism between prismatic slip and a Mg17Al12 precipitate was investigated by using molecular dynamics (MD) simulations and modified embedded-atom method (MEAM) potentials for Mg-Al alloys. The precipitate and the matrix satisfy the Burgers orientation relationship. Under tensile strain, prismatic dislocations were activated and these dislocations were slightly dissociated with a narrow stacking fault. It was found that the prismatic dislocations were able to shear through the precipitate during deformation, and created an observable shear offset in the precipitate. This mechanism is significantly different from the interaction between a basal dislocation and a precipitate where the precipitate cannot be plastically sheared by the basal dislocation. Our calculations show that the critical resolved shear stress (CRSS) of the prismatic slip is about two to three times higher than that of the basal slip. When the local shear stress exceeds the yield stress of the precipitate, the prismatic dislocations may shear through the precipitate.