Microstructural Evolution and Mechanical Properties of 2219 Aluminum Alloy Deposited by Wire and Arc Additive Manufacturing

Thin‐walled specimens of 2219 aluminum alloy are fabricated at different deposition speeds using the wire + arc additive manufacturing (WAAM) method. The effects of deposition speed on the microstructure, growth rate of columnar grains, and tensile strength of WAAM‐printed Al–Cu alloys are investigated. The fraction of columnar grains decreases from 86.7% to 12.2%, and the average grain size decreases from 147 to 65.3 μm as the deposition speed increased. Also, the fraction of θ phase gradually decreases as the deposition speed increased. Specifically, the growth rate of columnar grains varies from 1.02 × 10 −3 to 2.05 × 10 −3 m s −1 , which possesses two orders of magnitude higher than the growth rate of equiaxed grains. With increasing the loading stress, the cracks first form on the dendritic θ phases located at the grain boundaries, reducing the effective loading area. With the deposition speed increased, the typical dimple‐like structures are presented at the fracture surfaces, attributing to a decrease in Cu content at the grain boundaries and the producing of the spot‐like θ phase inside the matrix. The specimen with a deposition speed of 250 mm min −1 possesses a tensile strength around 274 MPa, and the corresponding elongation reaches to 12.6%.