Improvement of mechanical properties of aluminium–copper alloy (AA2219) GTA welds by Sc addition

Abstract

Aluminium alloy AA2219 is a high strength alloy widely used for aerospace application. One of the drawbacks of most of the high strength aluminium alloys is that they suffer from poor weldability. However, AA2219 is an exception due to the presence of more copper 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 different gas tungsten arc welding (GTAW) techniques and modify the filler chemistry with addition of scandium (Sc) and zirconium (Zr) in order to improve the mechanical properties of the AA2219 weld joints. The application of the GTAW DCEN with Sc and Zr to the filler wire proved to be the most economical and perhaps the optimal choice for welding AA2219 aluminium alloys. Addition of Sc and Zr to the fusion zone during welding enhanced grain refinement in the GTAW welds leading to better mechanical properties when compared to welding with conventional AA2319 filler.

Keywords:

• ALUMINIUM–COPPER ALLOY
• GTA WELDS
• SCANDIUM
• MECHANICAL PROPERTIES