Effect of Arc Mode on Laser-Arc Hybrid Additive Manufacturing of Al-Cu Alloy: Pore Defects, Microstructure and Mechanical Properties

Laser-arc hybrid additive manufacturing (LAHAM) of Al-Cu alloy was carried out, the effects of different arc modes on pore formation, microstructure characteristics and tensile properties were investigated. The addition of high-frequency pulse current and cyclic polarity reversal for CMT-PADV mode was beneficial to the reduction of pores. Compared with CMT and CMT-P modes, the columnar grains were transferred to equiaxed grains for CMT-PADV mode, with the smallest grain size of 26.6 μm, highest fraction of high-angle grain boundaries up to 84.2%, and longest length of grain boundaries achieving 14.9 cm. Moreover, the eutectic was generated along the grain boundaries for the samples employing CMT and CMT-P modes, while was disrupted and intermittently distributed for CMT-PADV mode. In this case, the excellent mechanical properties were obtained for CMT-PADV mode, with tensile strength and elongation 276.6 MPa and 23.82% in horizontal directions, 262.9 MPa and 20.9% in vertical directions, respectively.