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

Chemical heterogeneities which build up during dendritic solidificatio n of metallic alloys are of great importance to their service properti es. In nominally single-phase alloys, off-equilibrium eutectic often a ppears which is associated with large compositional changes in the pri mary phase at the scale of the solidification microstructure. Tn order to obtain a precise description of solute heterogeneities, it has bec ome common practice to draw distribution curves obtained from numerous microprobe point counts. The experimental distribution curves show di fferences with respect to the usual predictions, these differences bei ng related to the sign of curvature at low solid fraction and to the a mount of highly segregated material at high solid-fraction. The presen t study is an attempt to investigate experimentally microsegregation b uild-up during solidification, and was carried out on an aluminium all oy quenched during directional solidification.