PREDICTION OF SOLUTE CONCENTRATION PROFILES FOR DISCONTINUOUS DISSOLUTION

The applicability of the Tu-Turnbull and Ziebo-Pawlowski diffusion mod els of discontinuous dissolution have been considered. The simulation procedure applied to the Ni-1.4 at.%. In alloy has shown a much better applicability of the Zieba-Pawlowski model than the Tu-Turnbull model for the prediction of the In concentration profiles left behind the r eceding reaction front. This comes from the fact that in the Tu-Turnbu ll model the same ratio between migration velocity and grain boundary diffusivity is assumed for both discontinuous precipitation and dissol ution processes. This is only true when the difference between tempera tures of discontinuous precipitation and subsequent discontinuous diss olution is relatively small. it has also been shown that the results o f simulation become better with an increase of the residual supersatur ation of the depleted alpha lamellae as well as with an increase of th e characteristic solute concentration left at the places where the bet a lamellae have just been dissolved.