Research on Technology of 7075 Aluminum Alloy Processed by Variable Polarity TIG Additive Manufacturing Utilizing Nanoparticle-Reinforced Welding Wire with TiB₂

TIG arc additive manufacturing experiments were performed utilizing TiB₂ nanoparticle-reinforced toward to 7075 aluminum alloy welding wire, and the microstructure and mechanical properties corresponding to different locations of welding plate were investigated. At the top location of the deposited layer, the microstructure was characterized by fine dendrite induced by solidification, and equiaxed grain was predominant at the middle location. The grain size at the bottom location was obviously larger compared to the top and middle locations, and secondary-phase particles were homogeneously distributed at the grain boundary or inner grains. The mechanical properties at the top location of the deposited layer were most excellent compared to the middle and bottom locations, and the tensile properties and micro-hardness were decreased with the detected area varying from middle location to the bottom location. The excellent combination of fracture elongation and maximum of tensile strength corresponding to different locations on the deposited layer were determined to be 361.8 MPa with respect to the 7075 aluminum alloy welding wire, respectively, which was higher compared to the samples processed by general arc additive manufacturing process with tensile strength of (279.4 ± 5.3) MPa, indicating the TiB₂ nano-sized particles possessed certain enhancing effects on the investigated 7075 aluminum alloy.