TWI

Friction stir welding (FSW) was employed to fabricate hybrid joints between wrought AA 5454 aluminium alloys and AZ 91 die cast magnesium alloys, and the weldability, microstructure, mechanical properties, corrosion and fracture behaviour of the welded joints were investigated. FSW was performed using a modified milling machine at a rotational speed of 280 rpm, welding force of 13 kN, tilt angle of 3 degrees and feed rate of 10 mm/min. Some welds were made by combining FSW with ultrasonic welding. Welded joint microstructure was observed by optical microscopy and SEM. Microhardness, tensile properties, and corrosion behaviour in NaCl solutions were determined. Fracture surfaces were examined by SEM. Issues discussed include the composition of interfacial interlayers, multiphase onion ring structure in the nugget, the effect on joint strength of ultrasonic oscillations during the welding process, and corrosion at the interface between the nugget and the Mg alloy.

9th International Symposium, 15-17 May 2012, Session 10B: Non Ferrous, Paper 01