The Concept of Electrically Assisted Friction Stir Welding (EAFSW) and Application to the Processing of Various Metals

Abstract : This report introduces a novel variant of conventional friction stir welding (FSW). Since 1991, friction stir welding provides an alternative to arc welding as a metal joining method in numerous applications. In FSW, the heat required to soften the target metal is generated totally by the rotating friction of the tool which necessitates rather high downward (Z) operating force and often leads to relatively short tool life. In the proposed modification, an electric current is added through the tip which provides ohmic heating of the work piece in its vicinity. This additional contribution combines with the tool rotation to produce Electrically Assisted Friction Stir Welding (EAFSW) and reduces frictional forces required of the tool to produce softening of the work piece metal. This can result in reduced tool wear, lower applied Z force and potentially higher weld speed. The reduction in Z force requirement, in particular, might enable construction of a smaller, more portable FSW machine having similar weld capabilities as the current large units. The machine modification/configuration is described. Experiments with various work piece metals and tool materials are discussed. Representative pictures of the resulting welds are presented. Finally, some conclusions regarding the possible scope and advantages of this new weld method are drawn.