Wire arc additive manufacturing of Al-Zn-Mg-Cu alloy: Microstructures and mechanical properties

Wire arc additive manufacturing (WAAM) is a promising approach to producing large-scale metal structures. The investigation on the WAAM of aluminum alloys has lasted for over 17 years and covered multiple alloy systems. However, fundamental research on the WAAM of quaternary Al-Zn-Mg-Cu alloys is still lacking. This study focuses on understanding the microstructural characteristics and mechanical properties of an ultra-high-strength Al-Zn-Mg-Cu alloy fabricated by WAAM. A single-pass multilayer component is successfully fabricated. Results indicate that a single deposition layer consists of two types of columnar grains with different textures and origins. Nanoscale second phases are observed to precipitate during the manufacturing process with location-dependent sizes and volume fractions due to different thermal histories. The microhardness of the cross-section exhibits a special un-uniform distribution between 75–164 HV_0.2 from the substrate to the top of the component. The WAAM deposited component shows higher overall tensile properties than the as-fabricated spray formed counterpart. The average yield strength and ultimate strength are higher in the vertical direction than in the horizontal direction, while the difference in elongation is small.