Local nonequilibrium effect on undercooling in rapid solidification of alloys

A local nonequilibrium approach to rapid solidification of undercooled alloys is presented. Taking into account the finite speed of mass signals, a steady-state solution to the nonisothermal rapid solidification problem has been obtained. We have found that, if the solidification front moves at a velocity V equal to or higher than the diffusive speed ${\mathrm{V}}_{\mathrm{D}}^{\mathrm{L}>}$ in the liquid, a partitionless thermal-controlled situation takes place. The solidification mechanism changes at V=${\mathrm{V}}_{\mathrm{D}}^{\mathrm{L}>}$ and the constitutional undercooling is lacking ahead of the solidification front. Some comparisons with the known experimental and theoretical results are discussed.