Comparative study on microhardness between friction stir welding and tungsten inert gas assisted friction stir welding of pure copper

Welding copper and its alloys is usually difficult to achieve by conventional fusion welding processes because of high thermal diffusivity of copper, which is at least 10 times higher than most steel alloys. In order to reduce the increased temperature loss, it would be advantageous to use a process that is carried out at lower temperatures. Friction Stir Welding (FSW) is a solid state joining process that involves the joining of two metal pieces at the molecular level without melting and was explored as a feasible welding process. In order to achieve an increased welding speed and a reduction in tool wear, this process is assisted by another one (TIG - tungsten inert gas) which generates and adds heat to the process. The research includes two experiments for the FSW process and two experiments for TIG assisted FSW process. It is presented the evolution of the temperature and of the axial force during the process and is determined the microhardness for each experimental case. The aim of this paper is to make known the effects of using TIG assisted FSW process on the microhardness of the pure copper joints and to present some conditions in which it is less affected