Microstructure and mechanical properties of 7A48 aluminum alloy fabricated by the wire-arc additive manufacturing + micro forging hybrid process

Abstract

Wire-arc additive manufacturing technology has been widely recognized as a suitable method for fabricating large-size, complex, and high-strength aluminum alloy components. Two components were obtained by adopting a self-made low Cu 7A48 wire under the deposition parameters (a voltage of 18 V, a current of 85 A, a welding speed of 9 mm/s, and an argon flow rate of 23 L/min). One was the wire-arc additive manufacturing component of Al–Zn–Mg–Cu alloy, and the other was obtained via WAAM + micro forging hybrid process with about a 35% forging reduction ratio. Compared to that of the single wire-arc additive manufacturing component, the porosity of the micro forging component was reduced by 78.6%, and the micro forging hybrid process averagely increased the ultimate tensile strength and elongation by 23.3% (360.6 MPa) and 209.8% (18.9%), respectively. Besides, both the fracture modes were ductile fractures. The microstructure of the wire-arc additive manufacturing component consisted of the coarse grain area and fine grain band. For the micro forging component, the grains were equiaxed and obviously refined, and the average grains size was reduced by 81.6%. After the micro forging hybrid process, the grain orientation tended to be unified from disorder, and the maximum texture index reduced from 5.69 to 4.08. In addition, the secondary T (Al2Mg3Zn3) phase in two components precipitated along the grain boundary.