Friction welding process of 5052 aluminium alloy to 304 stainless steel

Type 5052 aluminium alloy was joined to type 304 austenitic stainless steel via a continuous drive friction welding process. The joint strength increased, and then decreased after reaching a maximum value, with increasing friction time. Joint strength depended on the size and shape of the tensile testpiece. Friction weldability could be estimated by electrical resistmetry. The process of friction welding between the aluminium alloy and the stainless steel is proposed to evolve as follows: welding progresses from the outer to the inner region; an unbonded 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. 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 unbonded region and a thin reaction layer formed along the entire weld interface.