Microstructure refinement and mechanical properties enhancement of wire-arc additive manufactured 2219 aluminum alloy assisted by interlayer friction stir processing

High strength and ductility wire-arc additive manufacturing (WAAM) 2219 aluminum alloy have been fabricated with the assist of interlayer friction stir processing (FSP). The FSP brings about a significant microstructure refinement where the average grain size reached to about 5.2 mu m. As compared to the WAAM counterpart, the microhardness, yield strength, and ultimate tensile strength of the WAAM + interlayer FSP component are increased from 65.3 +/- 2.8 HV, 96 +/- 2 MPa and 249 +/- 3 MPa to 70.6 +/- 3.4 HV, 106 +/- 3 MPa and 278 +/- 4 MPa, respectively. Meanwhile, the elongations along the horizontal and vertical direction are increasing to 23.7 +/- 2.5% and 15.6 +/- 1.3%. The improvement in the mechanical properties of the WAAM + interlayer FSP components can be attributed to the remarkable grain refinement, broken-up of the second phase and elimination of pores induced by interlayer FSP deformation.