The contribution deals with clinching, which is cold joining technology of thin-walled structures. Clinched joints are commonly loaded by static or cyclic forces. As the use of clinch joints is increasing, detailed knowledge of material response to deformation used within the joint production as well as withing operational loading is required. Microstructure of base material and its changes due to clinching process and due to cyclic mechanical loading are investigated by metallography, micro hardness mapping and advanced scanning electron microscopy.