Simulation of the Si Precipitation Process in Mg₂Si Using a Phase-Field Kinetic Model

Abstract

The Si precipitation process in an Mg₂Si matrix has been simulated by the phase-field kinetic model, considering the eigen strain at the interface between precipitates and the matrix. We observed that the shape of the precipitate changed during the course of heat treatment from circular to lenticular. As the Si precipitate grew larger, the adjacent precipitate aggregated to form a lamellar microstructure. This microstructure is suitable for thermo-electric materials because the scattering of phonons will frequently occur at the interface between the Si precipitates and the Mg₂Si matrix. Our present simulation suggests drastic improvements of thermo-electric properties of this type of material are possible due to the eigen strain.

Fig. 1 Microstructural evolution of the Mg₂Si-Si binary system: (a) at the 120 time step, (b) at the 1200 time step, (c) at the 3600 time step and (d) at the 6000 time step. The inserted color scale represents the value of s₁ which represents the occurrence probability of Si precipitates. That means, the locations colored by red (s₁ = 1) are occupied by pure Si precipitates, those colored by blue Mg₂Si matrix.