PHASE FIELD SIMULATION ON MORPHOLOGY OF CONTINUOUS PRECIPITATE Mg 17 Al 12 IN Mg-Al ALLOY

Abstract

The morphology evolution of the continuous precipitate Mg_(17)Al_(12) in aging process was studied using KKS phase field model.In the model,the chemical free energy and chemical potential for the precipitate phase and matrix were obtained by using Thermo-Calc software and database.The effects of interfacial energy anisotropy were taken into account by introducing interface anisotropy function, and the effects of micro elastic strain energy were introduced based on the theory of micro elastic strain energy formulated by Khachaturya.It is demonstrated that the precipitate phase has a lath shape when only the interfacial energy anisotropy was considered regardless of the micro elastic strain energy. The precipitate phase grows into a diamond shape when only the micro elastic strain energy was taken into account regardless of the interfacial energy anisotropy.When both the effects of the interfacial energy anisotropy and the micro elastic strain energy were considered in the simulation,the precipitate phase has a lath shape with lozenge ends,which is in agreement with experimental observations.The interfacial energy anisotropy affects the overall morphology of the precipitate,and combining the interfacial energy anisotropy and the micro elastic strain energy results in the lath shape with lozenge ends.