Orientation and Microstructure Evolution of Al-AlCu Regular Eutectic Lamellar Bifurcating in an Abruptly Changing Velocity under Directional Solidification.

In an abruptly changing velocity under directional solidification, microstructures and the growth orientation of Al-AlCu eutectic lamellar were characterized. The change in solidification rate led to an interfacial instability, which results in a bifurcation of the eutectic lamella into new, refined lamellae. The growth orientation of the eutectic AlCu phase was also only in its (001) direction and more strongly oriented to the heat flow direction. The results suggest that the eutectic lamellar Al-AlCu bifurcation and the spacing adjustment may be caused by the rate determining lateral diffusion of the solutes after interfacial instability.