Comparative Study on Wire-Arc Additive Manufacturing and Conventional Casting of Al-Si Alloys: Porosity, Microstructure and Mechanical Property

Here, we compare the porosity, microstructure and mechanical property of 4047 Al-Si alloys prepared by wire-arc additive manufacturing (WAAM) and conventional casting. X-ray microscopy reveals that WAAM causes a higher volume fraction of gas pores in comparison with conventional casting. Effective refinements of alpha-Al dendrites, eutectic Si particles and Fe-rich intermetallic compounds are achieved by WAAM, resulting from its rapid solidification process. Both ultimate tensile strength (UTS, up to 205.6 MPa) and yield stress (YS, up to 98.0 MPa) are improved by WAAM at the expense of elongation after fracture. The mechanical property anisotropy between scanning direction and build direction is minimal for alloys via WAAM. Additional microstructure refinement and strength enhancement are enabled by increasing the travel speed of welding torch from 300 to 420 mm/min.