A dynamic Ising model, using effective cluster interactions, has been implemented to model the kinetics of phase separation in a Ti-15 at.% Al alloy. Cluster interactions are defined over clusters containing up to six atoms. The model predicts the rapid development of ordered α2D019regions prior to phase separation. The number and size of the ordered domains are correlated to the reduction in matrix super-saturation. The simulations predict that the α2-phase will form a complex interconnected microstructure.