Influence of deposition strategy and heat treatment on mechanical properties and microstructure of 2319 aluminium WAAM components

There is an increasing interest in additive manufacturing of high strength aluminium alloys built with wire and arc additive manufacturing (WAAM) technologies. Al-Cu alloys are susceptible to hot cracking, however, pulse advanced cold metal transfer (CMT-PADV) welding process ensures a low heat input that avoids this defect while reducing the part porosity. This study has demonstrated that porosity below 1 % does not affect mechanical properties of 2319 WAAM walls, whereas the as-built microstructure and applied heat treatment highly influence the properties obtained. Without interlayer dwell time, a fine uniformly distributed equiaxed microstructure is obtained, however, if an interlayer arc stop period is applied, columnar dendritic grains in the interlayer zone is obtained. Heat treatment with low aging temperature and time demonstrated not to be suitable to ensure high mechanical properties and low anisotropy. Instead, if 190 °C and 26-hour aging heat treatment is used, properties up to 324 MPa for yield stress, 452 MPa tensile strength and 8 % elongation can be achieved perpendicularly to the building direction with anisotropy of 1 %, 2 % and 46 %, respectively, for the manufacturing conditions that avoided columnar grains. This fact was critical to ensure highest strength and ductility values and low anisotropy.