The influence of convection on the duration of the initial solute transient in alloy crystal growth

Our purpose in this work is to analyse in some detail the influence of conv ection on the formation and the build-up of the solutal boundary layer duri ng the initial composition transient. Our main assumption is that the alloy is sufficiently dilute for the variation of the interface temperature to b e neglected, in other words that the solidification interval is small enoug h. In order to thoroughly characterise the problem, we use a coupled theore tical analytical and scaling analysis and numerical approach. Comparison wi th existing experimental data is also provided. The effect of convection is seen to be adequately accounted for owing to the convecto-diffusive parame ter Delta. The overall agreement observed allows us to propose a simple rul e of thumb expression for the extent of the initial composition transient. (C) 2000 Elsevier Science B.V, All rights reserved.