EXPERIMENTAL INVESTIGATION OF THE DEVELOPMENT OF MICROSEGREGATION DURING SOLIDIFICATION OF AN AL-CU-MG-SI ALUMINUM-ALLOY

Chemical heterogeneities which build up during dendritic solidification of metallic alloys are of great importance to their service properties. In nominally single-phase alloys, off-equilibrium eutectic often appears which is associated with large compositional changes in the primary phase at the scale of the solidification microstructure. Tn order to obtain a precise description of solute heterogeneities, it has become common practice to draw distribution curves obtained from numerous microprobe point counts. The experimental distribution curves show differences with respect to the usual predictions, these differences being related to the sign of curvature at low solid fraction and to the amount of highly segregated material at high solid-fraction. The present study is an attempt to investigate experimentally microsegregation build-up during solidification, and was carried out on an aluminium alloy quenched during directional solidification.