Microstructure and mechanical properties of Sc modified Al-Cu alloy (AA2219) electron beam welds

Al alloy AA2219 is a high strength alloy belonging to the 2000 series Al alloys widely used for aerospace application. One of the drawbacks of most of the high strength Al alloys is that they suffer from poor weldability. However AA2219 is an exception due to the presence of more Cu that helps in healing cracks by providing extra eutectics. Although AA2219 has excellent weldability the strength of a welded joint is only 35-45% of the base metal. The loss of strength is due to the dissolution of the strengthening precipitates during melting. Therefore, there is a need to improve the fusion zone strength of AA2219 welds. In this study an attempt was made experimentally to use electron beam welding and modify the base metal chemistry with addition of Sc and Zr in order to improve the mechanical properties of the AA2219 weld joints. Fine equiaxed microstructure was obtained in the fusion zone of electron beam welds with improved mechanical properties. Eutectic was found to be distributed discontinuously which resulted in improved yield strength, tensile strength and ductility compared to welds made without Sc and Zr. © 2008 Institute of Materials, Minerals and Mining.