Quasi-Isotropy Structure and Characteristics of the Ultrasonic-Assisted WAAM High-Toughness Al Alloy

Abstract

Wire Arc Additive Manufacturing (WAAM) has emerged as a highly promising method for the production of large-scale metallic structures; nonetheless, the presence of microstructural inhomogeneities, anisotropic properties, and porosity defects within WAAM Al alloys has substantially hindered their broader application. To surmount these obstacles, ultrasonic-assisted WAAM was applied in the fabrication of thin-wall structures utilizing 7075 Al alloy. This study investigates the effects of ultrasonic-assisted Wire Arc Additive Manufacturing (WAAM) on the structural and mechanical properties of 7075 Al alloy specimens. Microstructural analysis showed a significant refinement in grain distribution, with the average grain size notably reduced, enhancing the material’s homogeneity. Porosity across the specimens was quantified, showing a decrease in values from the upper (0.02151) to the middle (0.01347) and lower sections (0.01785), correlating with the rapid cooling effects of WAAM. Mechanical testing revealed that ultrasonic application contributes to a consistent hardness pattern, with measurements averaging 70.71 HV0.1 horizontally and 71.23 HV0.1 vertically, and significantly impacts tensile strength; the horizontally oriented specimen exhibited a tensile strength of 236.03 MPa, a yield strength of 90.29 MPa, and an elongation of 31.10% compared to the vertically oriented specimen which showed reduced mechanical properties due to the presence of defects such as porosity and cracks. The fracture morphology analysis confirmed a predominantly ductile fracture mode, supported by the widespread distribution of dimples on the fracture surface. The integration of ultrasonic vibrations not only refined the grain structure but also modified the secondary phase distribution, enhancing the quasi-isotropic properties of the alloy. These results underline the potential of ultrasonic-assisted WAAM in improving the performance of the 7075 Al alloy for critical applications in the aerospace and automotive industries, suggesting a promising direction for future research and technological advancement in additive manufacturing processes.