Solidification and segregation behaviors in 6061 aluminum alloy

The characteristics of a solid/liquid interface established during directional solidification were investigated in a 6061 aluminum alloy (Al6061 alloy) in which interface patterns, such as planar, cellular and dendritic, form in the mushy zone. Directional solidification experiments were carried out in alumina tubes with an inner diameter of 5 mm to obtain the different microstructures for varying growth rates under an imposed thermal gradient of 9.45 K/mm. As a consequence, primary arm spacing, secondary arm spacing and the length of primary arm were measured for steady-state growth conditions. Furthermore, the solute concentration profiles for the final solidification region were obtained using a SEM-EDS system in order to examine the segregation behaviors of alloying elements. Therefore, it was found that the degree of segregation in the Al6061 alloy was dependent on the growth rate under given solidification conditions, that is, the elemental segregation became more severe with increasing growth rate in the interdendritic region.