Porosity suppression and mechanical property improvement of wire-arc directed energy deposited TiC_p/Al-Cu alloys joint by oscillating pulsed wave laser beam welding

Hybrid manufacturing technology combining wire-arc directed energy deposition (WA-DED) and laser beam welding (LBW) presents a promising avenue for efficiently manufacturing large-size aluminum alloy components. The high tendency of porosity defects, particle decomposition, and fusion zone softening are outstanding challenges in the LBW welding of additively manufactured particle-reinforced aluminum alloys. Herein, a WA-DED-processed Al-6.3Cu alloy embedded with 0.6 wt% TiC particles was employed as weldment. Four different laser beam modes, including continuous wave (CW), pulsed wave (PW), oscillating continuous wave (OCW), and oscillating pulsed wave (OPW), were used to join TiC_p/Al-6.3Cu alloy. The effects of different laser modes on the porosity defects, microstructure evolution, and mechanical properties of WA-DED particle-containing aluminum alloy joints were studied comparatively. Multi-scale characterization results showed that the enhanced molten pool flow via laser beam modulation effectively suppressed porosity defects and facilitated the uniform particle distribution. The OPW mode provides an optimal effect on porosity inhibition and weld microstructure refinement compared to the pulsed or oscillating modulation modes. The heat-treated LBW joint via OPW mode achieved excellent comprehensive mechanical properties, whose elongation and ultimate tensile strength reached 9.5% and 449 MPa, respectively. This enhanced performance can be attributed to the decreased porosity, refined weld microstructure, and high-density nano-precipitation. This study provides fundamental guidance for the welding of high-strength Al-Cu alloy fabricated by additive manufacturing.