Friction-based processes for hybrid multi-material joining

The adoption of multi-material lightweight structures has been recognized as one of the most effective and promising solutions to improve fuel efficiency and accelerate the electrification of future transportation systems. A wider application of multi-material lightweight structures has been limited by our capability to fabricate them reliably and cost-effectively at a commercial scale. In the last decade, many friction-based joining processes have been developed and demonstrated their advantages over mechanical fastening and adhesive bonding processes in fabricating future multi-material lightweight structures. This article provides a comprehensive review on the recent advances of five promising friction-based joining processes (friction assisted joining, friction lap welding, friction spot joining, friction riveting, and ultrasonic welding) on the aspects of facilities, joining process, joining mechanism, applicable materials, surface pretreatments, and the influence of process parameters on the performance of the produce joints. This article also provides a summary of the performance of the produced joints under static load, dynamic load, various thermal cycles, or harsh chemical environments. The main similarities and differences among the joining processes are discussed. The paper points out the main knowledge gaps that need to be filled and the research that needs to be conducted to further advance the joining process. This review article will place the friction-based joining process at a new starting point with accelerated developing speed towards higher technical maturity to make the processes available for certifiable industrial applications.