The process chain of die casting and hot extrusion for the fabrication of cohesively bonded aluminum bilayer billets was investigated. It represents an energy- and material-efficient link between casting and forming technologies for the production of load-adjusted lightweight constructions. Commercial aluminum AA7075 and AA6060 were initially jointed by die casting. The influence of various process parameters, such as die temperature and cooling conditions, on the interface formation was analyzed. Remelting and recrystallization processes as well as the diffusion-driven interaction between the joining partners were identified as major bonding mechanisms. As-cast bimetal billets were subsequently post-processed using hot extrusion. The present paper shows the interface evolution over the process chain of casting and massive forming.