Abstract
The mechanical and metallurgical properties of friction welded joints between type 5052 aluminium alloy and type A36 steel have been studied in the present work. Joint strength increased with increasing upset pressure and friction time until it reached a crictical value. The strength of the joint settled at a lower value, compared with that of the base metal, in the case of increasing friction time, caused by the formation of an intermediate phase (intermetallic compound, oxides). The microstructure of 5052 alloy was greatly deformed near the weld interface, and underwent dynamic recrystallisation owing to frictional heat and deformation resulting from the friction welding process. Therefore, a very fine and equiaxed grain structure was observed near the interface. Elongated grains were observed outside the dynamic recrystallisation region at the peripheral part, while the A36 steel side was not deformed. The hardness of the near interface was slightly softer than that of the 5052 alloy base metal, and maximum softened width was ∼8 mm from the interface. In the present work, the conditions of friction time t 1 = 0.5 s and upset pressure P 2 = 137.5 MPa gave maximum joint strength of 202 MPa when the friction pressure, upset time and rotation speed were fixed at 70 MPa, 5 s and 2000 rev min-1, respectively, and these were the optimum friction welding conditions for the aluminium alloy 5052-A36 steel joint.
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