In lightweight design, clinching is a cost efficient joining method, especially for different joined materials and thicknesses. The quality of such a joint is usually evaluated by ex-situ destructive testing methods. These methods, however, do not yield the detection of phenomena occurring during the joining process such as elastic deformations and cracks that close after unloading. Alternatively, in-situ computed tomography (in-situ CT) can be used to investigate the manufacturing process of the clinch point depending on varying boundary conditions regarding process and material parameters. As the use of a classical clinching tool made of steel leads to strong artefacts and to a high attenuation, the image quality of CT scans is limited so far. The aim of this work is the identification of materials or material combinations which allow CT measurements and are suitable as a clinching tool material. Therefore, mechanical requirements on the tool materials are identified, potentially CT-suitable tool materials are selected and numerically investigated. In the investigations, two lubricated aluminium sheets are single-step clinched to form a rotationally symmetric joint without cut section. The simulation model is verified by applying common quality criteria on the simulation results (undercut, bottom thickness, neck thickness). It is shown that e.g. silicon nitride and titanium β alloys are best suited for the punch, cermets and titanium α+β are suitable for the die, and fibre reinforced plastics can be selected for the blank holder tip.