Induction heated tool assisted friction-stir welding (i-FSW): A novel hybrid process for joining of thermoplastics

This paper presents a hybrid friction-stir welding process, i-FSW, for the joining of thermoplastics. In this process, the friction-stir tool during welding is heated by induction and the temperature is precisely maintained though feedback control. The paper conveys new observations on friction-stir welding of thermoplastics through a case study on the welding of high-density polyethylene plates. The mechanical behavior and weld microstructure were studied over a wide range of tool rotational speeds and tool-pin temperatures. A narrow transition zone between the weld and base materials without any defect ensures joints with a similar strength to the base material, vis-a-vis better than previously reported results with the same material. A drop in hardness at the weld zone, for all the parameters, and a transition from brittle to ductile nature of the joints at higher tool-pin temperatures were observed. The material flow and weld formation mechanism in i-FSW is discussed.