In the paper some potentialities of FE models of joining by forming operations were showed. In particular FSW and LFW processes were considered. Solid state welding processes are increasing their application in industrial environments due to their strong advantages with respect to traditional fusion techniques. Advanced FEM tools are requested in order to carry out a detailed engineering of the processes and to get quantitative results useful for the set up of the processes. Also basic investigations regarding process mechanics and material flow are important in order to fully understand the fundamental aspects of the processes and the bonding conditions at the interface of the specimens to be welded. In the paper Friction Stir Welding (FSW) and Linear Friction Welding (LFW) operations are considered and numerical results derived from FE models of the two processes are shown. The proposed results give the idea of the potentialities of the numerical tool for the two considered processes and in particular furnish interesting information on the actual bonding conditions at the welding zone.