Solidification microstructure selection in the Al-rich Al-La, Al-Ce and Al-Nd systems

摘要

The effect on solidification and microstructure of solidification conditions in wedge chill casting and Bridgman growth have been investigated for Al 5.7 to 19 wt/100 X (X=La, Ce, or Nd) alloys. The systems are shown to exhibit an asymmetrical zone of coupled eutectic growth on a plat of front velocity versus alloy composition. Only the equilibrium phases αAl and Al_11X_3 form under the conditions studied and the results are consistent with a eutectic composition of ￣12 wt/100 X for all three systems, as proposed in 1990 by Kononenko and Golubev. Both primary αAl and primary Al_11X_3 underwent significant morphological changes as the boundaries of he coupled zone were approached. The positions of these boundaries at high velocities yielded values of the growth parameters for primary Al_11X_3 and the αAl-Al_11X_3 eutectic similar in magnitude to recent measurements for corresponding primary phases and eutectics in the related Al-Fe and Al-Ni systems.