Joining of advanced high-strength steel to AA 6061 alloy by using Fe/Al structural transition joint

Abstract

Abstract Joining steel plates and aluminium plates by means of using Fe/Al structural (Triclad) transition joints has been well-received in the shipbuilding industry, but is rarely applied in other industries. In this work, 12.7 mm thick plates of advanced high-strength steel and AA 6061 alloy were successfully joined by using hybrid laser-arc welding with the help of Triclad transition joints. The parameters were optimized for welding dissimilar steels (A516 to advanced high-strength steel) and welding dissimilar aluminium alloys (AA 5456 to AA 6061). The optimization controlled the total heat input and kept the Al/Fe interface of the Triclad transition joint below the maximum allowable temperature of 315.56 °C in order to minimize the growth of brittle intermetallic phases and retain the mechanical properties of the Triclad transition joint. A finite element model was developed to study the temperature evolution at the Triclad interface and the heat distribution along the welded structure. A “4:1” ratio was used between the width of the Triclad transition joint and the thickness of the webs. This ratio improved the load-bearing property of the Triclad transition joint and compensated for the microcracks and brittle Al-rich intermetallic phases observed at the Triclad interface. Tensile strength of 220 MPa was achieved at the welded structure. The fracture occurred at the heat affected zone of the AA 5456-to-AA 6061 weld.