Friction Welding to Join Dissimilar Metals

The purpose of this work was to join and assess the development of solid state joints of dissimilar material AA6082 aluminum alloy and AISI 304 stainless steel, via continuous drive friction welding process, which combines the heat generated from friction between two surfaces and plastic deformation. Tests were conducted with different welding process parameters. The results were analyzed by means of tensile test, Vickers micro hardness test, fatigue test, Charpy vnotch impact test, and SEM-EDX (energy dispersive X-ray) analysis in order to determine the phases that occurred during welding. The strength of the joints varied with increasing friction pressure and friction time keeping upset pressure and upset time constant. The joint strength increased, and then decreased after reaching a maximum value, with increasing friction pressure and friction time. The process of friction welding between the aluminum alloy and the stainless steel is proposed to evolve as follows: welding progresses from the outer to the inner region; an unbounded region is retained at the centre of the weld interface with shorter friction time; longer friction time causes the formation of an intermetallic reaction layer at the weld interface and the reaction layer grows as the friction time increases. Some of the welds had poor strength due to the accumulation of alloying elements at the joint interface. When the thickness of the reaction layer increased above a critical value, the joint was brittle and fractured at the weld interface. The joint was sound when there was no unbounded region and a thin reaction layer formed along the entire weld interface.