Static strength and design of aluminium-to-steel thin welded joints

Welding together dissimilar materials, and, in particular, aluminium alloys to steel, has always been a challenge because of the significant difference in their mechanical, thermo-physical and metallurgical properties which causes the formations of hard and brittle intermetallic phases in the welding region. Recently, EWM® has developed a welding process known as ColdArc®, where the heat input and arc stability are precisely controlled. The present study was designed to investigate the static strength of aluminium-to-steel thin welded joints manufactured using EWM coldArc® welding technology. Butt, lap and cruciform welded connections were prepared to assess tensile strength and failure mode of these hybrid welded joints. The visual examination of the fracture surfaces revealed that, regardless of the geometry of the welded connections, the fracture of the joints always took place in the heat-affected zone (HAZ) on the aluminium side. This inspection indicated that the use of EWM coldArc® welding technology had improved the strength of the hybrid welded joint significantly and removed the problem of having a brittle phase in the welding zone. The results obtained from this investigation shows that Eurocode 9 can also be used to design aluminium-to-steel thin welded joints.