Al–Cu alloy fabricated by novel laser-tungsten inert gas hybrid additive manufacturing

Abstract

Owing to its high strength to weight ratio, Al–Cu alloy is extensively used in the aeronautic and aerospace industries. However, there are some shortcomings in the additive manufacturing of Al–Cu alloy, such as cracks and poor strength. In this work, Al–Cu (2219-Al) specimens with excellent mechanical properties were fabricated by laser-Tungsten Inert Gas (TIG) hybrid additive manufacturing. From the microstructural studies, the average grain size in the laser zone (LZ) decreased to 14.4 μm, which was approximately 40.3 % smaller than that in the arc zone (AZ). Under the influence of laser stirring, Cu in the LZ was distributed more uniformly than in the AZ. An incoherent θ phase, at the nanoscale, was discovered in both the AZ and the LZ. Its crystal orientation relationship was described as [110]α∥[002]θ, (110)α∥(002)θ between the α-Al matrix and the θ phase. The semi-coherent θ′ phase was observed in the LZ. Meanwhile, the θ′ phase characterized a good coherent relationship with the α-Al matrix, which resulted in low phase boundary energy. Furthermore, the deposited specimens exhibited a yield strength of 155.5 ± 7.9 MPa and an ultimate tensile strength of 301.5 ± 16.7 MPa, with an elongation of 12.8 ± 2.8 %. These mechanical properties were higher than in specimens fabricated by TIG, CMT and SLM methods. The improved properties were predominately related to the smaller size of eutectics, the uniform distribution of Cu and the semi-coherent θ′ phases in the LZ. The combined effect of laser and arc can yield components with excellent mechanical properties, promoting the material for an expansive range of applications.