B. Drevet et al., Solidification of aluminium-lithium alloys near the cell/dendrite transition-influence of solutal convection, J CRYST GR, 218(2-4), 2000, pp. 419-433
Directional solidification experiments were carried out on Al-12.3 at% Li a
lloys near the cell/dendrite transition. Experiments were performed both in
microgravity and on the ground in vertical upward configuration. Reliable
data for 3D solidification with a purely diffusive transport regime in the
liquid have thus been obtained that are used to test current theories relat
ive to primary spacing, tip undercooling and microsegregation. In particula
r, we show that the cell tips region can be satisfactorily described by the
Saffman-Taylor equation for viscous fingering. Further, comparison of grou
nd samples with those elaborated in microgravity has enabled the effects of
solutal convection to be evidenced, both at the macroscopic scale (solid/l
iquid front shape, macrosegregation) and at the microscopic scale (cell tip
composition, intercellular liquid fraction, primary spacing). (C) 2000 Els
evier Science B.V. All rights reserved.