SOLIDIFICATION IN THE ONE-DIMENSIONAL MODEL FOR A DISORDERED BINARY ALLOY UNDER DIFFUSION

The propagation of the solidification front of a binary alloy growing from its melt is studied by Monte-Carlo simulation and by analytical a pproximation methods. The simulation shows that in the one-phase regio n the alloy grows steadily with a velocity controlled solely by kineti cs. In the two-phase region, the previously reported anomaly for the d iffusionless growth is removed by the diffusion of atoms and the diffu sional t(1/2) growth law is confirmed at least in the range where the diffusionless process is slower than diffusion. We cannot rule out, ho wever, that the anomaly occurring in the diffusionless case persists e ven under diffusion, when the diffusionless growth asymptotically is f aster than a typical diffusion process. The Monte-Carlo simulations ar e compared with an approximate analytical description ignoring correla tions between the components.