EAGER: Feasibility Study of Hybrid Friction-Stir Riveting of Mg Alloys

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This EArly-concept Grants for Exploratory Research (EAGER) grant provides funding for the development of a new friction-stir riveting technique for joining hard-to-weld materials such as Mg and Al alloys, and dissimilar metals. In this method, a solid rivet is used as a friction-stir welding head for joining two pieces of materials which can be either sheets or bulk metals. An action of combined rotation and pressing pushes the rivet into the metals. After a predetermined depth is reached, the action stops and the rivet is left in the metals, forming a desirable mechanical joint. A solid bonding ring is also created at the faying interface. The locking mechanism, defect formation, and relationship between influential physical attributes and important strength measures of a joint will be investigated. A direct comparison between this and other joining methods such as self-piercing riveting and resistance spot welding will be conducted to validate this new joining method.The successful completion of this research will pave the way for a future proposal for a larger scale, in-depth study and optimization of this joining method. The basic understanding of the effects of materials including the base metal(s) and rivet, and design and process variables obtained will provide critical information for further development of this technique. A relationship linking the quality of a joint to easily measurable geometric attributes of the joint will be developed for quality inspection, and certain critical process parameters such as the profiles of torque and thrust during riveting may be used as a means for real time quality control. The ultimate goal of this research is to develop a robust, economical and industrial joining process to enable the use of advanced materials in sheet metal industry for energy saving and emission reduction.