Microstructural characteristics and mechanical properties of Al-Cu alloys fabricated via 8-shaped oscillating laser wire additive manufacturing

Abstract

Al–Cu alloy components fabricated by laser wire additive manufacturing (LWAM) generally present coarse columnar grains and poor mechanical properties. This study proposes a new strategy, integrating an 8-shaped beam oscillation and laser directed energy deposition, to solve these issues. The impacts of oscillation frequencies and amplitudes on the energy flux distribution and macro morphology of the single-bead deposited layer are investigated. The influences of beam oscillation on the microstructural characteristics and tensile properties of Al–Cu alloys fabricated by oscillating laser wire additive manufacturing (O-LWAM) are revealed. A high-frequency oscillating laser achieves a uniform energy flux distribution and improves the surface quality of the deposited layer. The <100> texture in the O-LWAM specimen decreases markedly owing to the columnar to equiaxed transition. The Cu element content at grain boundaries in the O-LWAM specimen is reduced by 52.6 %. The ultimate tensile strength of O-LWAM specimens in the horizontal and vertical orientations reach 334.2 and 327.3 MPa, respectively, which increased by 40.7 % and 64.6 % compared to those of the LWAM specimen. The substantial enhancement in strength and plasticity is attributed to fine-grain strengthening.