Grain refinement and improved mechanical properties of wire arc additive manufactured 2219 Al-Cu alloy by in-situ Ti alloying

In this study, a method combining the wire arc additive manufacturing (WAAM) with in-situ Ti alloying was developed to fabricate 2219 Al-Cu alloy. During the WAAM process, the Ti foil pre-positioned on the top surface of the depositing interlayer is added into the molten pool, enabling in-situ Ti alloying. A thin wall with a gradually increasing Ti content along the building direction was first fabricated to assess the appropriate Ti addition level. Subsequently, a thin wall containing the optimal Ti addition amount was fabricated. The influence of Ti addition on the microstructure and mechanical properties was then systematically investigated. The pre-positioned Ti foil supplies Ti atoms into the molten pool, where the Al₃Ti nucleants are formed through a reaction between Ti and Al atoms. The Ti atoms can also contribute to constitutional supercooling. These combined effects promote the grain refinement, resulting in a 62.4 % reduction in grain size. The Ti addition improves tensile strength without compromising elongation.