The influence of two solute elements (Ge and In) on the phase formation of CoCrCuFeNi thin films was studied. In both cases, a crystalline-to-amorphous phase transition is observed if the solute fraction is higher than a certain threshold. In the In-x-CoCrCuFeNi system, the phase transition could be understood from the lattice distortion, or stated differently from the atomic radius difference between In and the base elements. In the Ge-x-CoCrCuFeNi system, the phase transition is not topologically driven as the atomic radius of Ge is similar to the base elements. The amorphization threshold can, however, be predicted by the thermodynamic model of Miedema. This study demonstrates that the senary alloys could be regarded as binary alloys of the form X-x-TM1 (-) (x) (X = Ge or In, and TM = transition metals) and their phase formation can be explained by topological and/or thermodynamic considerations. (C) 2016 Elsevier B.V. All rights reserved.