COMPUTER-SIMULATION OF SPINODAL DECOMPOSITION IN TERNARY-SYSTEMS

The non-linear spinodal decomposition kinetics of a quenched homogeneous ternary alloy within three- or two-phase fields is modeled using a computer simulation technique formulated in the reciprocal lattice. Based on two-dimensional computer simulations, it is shown that, similar to binary alloys, spinodal decomposition in a ternary system usually produces interconnected morphologies at the very early stages of decomposition. For most of the compositions investigated, a decomposition of a homogeneous phase into three phases takes place in two stages. For some compositions, the two stages are the phase separation of an homogeneous phase into two phases, followed by further phase separation of one of the two phases into another two phases, resulting in a three-phase mixture. For other compositions, the first stage is a phase separation of an initially homogeneous phase into a two-phase mixture followed by a second stage, the appearance of a third phase along the existing interphase boundaries. This sequential phase separation in a ternary alloy can be justified from a thermodynamic stability analysis combined with the knowledge of the thermodynamic driving force for phase separation. It is also demonstrated that a third minor component strongly segregates to interphase boundaries during spinodal decomposition and subsequent coarsening of a homogeneous ternary alloy into two phases.