We present an investigation of structural changes occurring in bilayer stacks with crystalline columnar growth when one of the layers is substituted by layers known to grow amorphous. In Co/Cu multilayers the Co layers were substituted by CoZr layers of varying Zr content and layer thickness. Structural characterisation was performed by transmission electron microscopy (TEM). We show that the amorphisation of the CoZr layers leading to a destruction of the columnar growth depends both on the Zr content and on the thickness of the CoZr layers. Additionally a change to textured growth with a <111> normal to the substrate occurs with increasing Zr content. We explain our observations by a simple picture based on the hard sphere model.