A Review of Joining Processes for High Strength 7xxx Series Aluminum Alloys

The applications of high strength aluminum alloys in automobile manufacturing has been growing with increasing demands for fuel efficiency and reduction of CO2 emissions. Aluminum alloys pair a high specific strength with relatively low cost compared to similar lightweight metals. The 7XXX series aluminum alloys in particular exhibit a high strength in excess of 500 MPa after heat treatment. However, these alloys exhibit poor weldability because of their high crack susceptibility, high thermal expansion coefficient, and low vaporization-temperature of alloying elements such as Zn and Mg, which readily contributes to weld defects such as cracks and porosity. In this paper, the mechanical properties and microstructural characteristics of 7XXX aluminum alloys are related to welding processes and reviewed for better understanding of the welding characteristics of this high strength alloy.