Numerical modeling and experimental investigation on plasma-assisted hybrid friction stir welding of dissimilar materials

Plasma-assisted friction stir welding (P-FSW) is a solid state joining process that preheats the high melting temperature material ahead of FSW tool and enhances the material flow to improve the weld quality. Quantitative calculation by a sophisticated mathematical model of hybrid friction stir welding for dissimilar materials is a daunting task due to complex issues like mixed property in the weld zone, flow mixing action and solid state phase transformation. A 3D finite element based phenomenological model is developed to study various aspects of P-FSW between aluminum and copper. A dedicated heat generation model at various contact conditions between tool and workpiece, and a Gaussian distributed heat flux from plasma arc is used for the simulation. In weld zone, the impression of time-varying functionally graded material (FGM) is used for material behavior. The numerical model results are validated with experimental measurement of P-FSW in terms of time-temperature history and computed isotherm of nugget zone. Relatively better agreement shows the robustness of the developed numerical model. The reliability analysis of the model is performed at various welding conditions. The effect of preheating by plasma source is analyzed by microstructural phenomena. (C) 2015 Elsevier Ltd. All rights reserved.