5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

We present an in situ experimental study of crystallographic effects during lamellar- eutectic growth in thin Al-Al2Cu samples. The Al-Al2Cu alloy is known to form eutectic-grain dependent lamellar eutectic microstructures, and to present special, or heteroepitaxy orientation relationships (OR) between the eutectic crystals. The term crystallographic effects refers here to a marked dependence of the growth microstructure on the orientation of the two solid phases relative to each other, and the direction of growth. We prepared thin (≈10 µm thick) metallic films by plasma sputtering on sapphire plates. The thin-sample geometry allows one to observe lamellar-growth patterns in real time without convection in the liquid, by using a long distance optical microscope (reflected-light mode) focusing the contact surface of the metallic film with one of the transparent substrates. We could identify both « floating » grains with a regular dynamic behavior in steady-state, and locked grains, within which the lamellae grow inclined, parallel to a fixed direction. We combined our optical observations with ex situ crystallographic analyses usign two methods, namely, x-ray diffraction and EBSD in order to determine the ORs in the different eutectic grains. We will comment on our results in the light of a recent work on the effect of an anisotropy of the surface free energy of the interphase boundaries on lamellar eutectics.