ON THE ASSUMPTION OF AN ADDITIVE EFFECT OF SOLUTE ELEMENTS IN DENDRITE GROWTH

The individual effect of some common alloying elements on the dendrite growth conditions in aluminium-silicon tasting alloys has been invest igated by measuring the dendrite coherency point. Tn the existing theo ries for dendrite growth it is usually assumed that the effect of the solute elements is additive, and one purpose of the present investigat ion is therefore to investigate this approach. The effect of successiv e additions of Mg, Fe and two levels of grain refinement, by AlTi5B1, on dendrite coherency has been investigated in two AlSi alloys; AlSi7 and AlSi11. By changing the order of addition of these elements, tile assumption of an additive effect is verified. The results show that tw o separate parameters are altered with the alloying additions: the gra in size and the dendrite growth rate, both being very important for th e solidification characteristics. When the effect on grain size is con sidered separately, there is a good qualitative correspondence between the theoretical predictions and the experimental results. (C) 1997 El sevier Science S.A.