In a groundbreaking study published in *Materials Research Express* (translated as *Materials Research Express*), researchers from the Department of Materials Engineering at Jiangsu University of Technology in China have unveiled significant advancements in the fabrication and heat treatment of 7075 aluminum alloy components using Wire Arc Additive Manufacturing (WAAM). Led by Yiqi Wang, the research team explored the microstructure and mechanical properties of thin-walled 7075 aluminum alloy samples, offering promising insights for the energy sector and beyond.
The study focused on the additive manufacturing of 7075 aluminum alloy samples using a self-developed welding wire and metal inert gas (MIG) welding. The samples underwent a solid solution treatment followed by a double-stage aging heat treatment. The researchers employed various analytical techniques, including optical microscopy, electron backscatter diffraction, scanning electron microscopy, and energy dispersive spectroscopy, to investigate the metallographic structure, precipitate phases, and mechanical properties of the samples before and after heat treatment.
“Without heat treatment, the grains in the WAAM 7075 aluminum alloy samples exhibited a distinct weld structure with noticeable orientation,” explained Yiqi Wang, the lead author of the study. The researchers observed that precipitated phases such as η (MgZn₂), S (Al₂CuMg), and T (AlZnMgCu) formed along the grain boundaries, with high-melting-point compounds like AlMnFeSi, Al₁₃Fe₄, and Mg₂Si serving as nuclei. These weak fusion zones between adjacent weld beads contributed to poor mechanical properties in the as-deposited state.
However, the story takes a promising turn with the application of heat treatment. “After heat treatment, the η, S, and T phases were completely dissolved into the matrix, resulting in solid solution strengthening and aging,” Wang noted. The interlaminar fusion zone (IFZ) grains recrystallized into equiaxed structures, significantly improving the tensile strength and elongation in the cladding direction to 464.2 MPa and 13.11%, respectively.
The implications of this research for the energy sector are substantial. The enhanced mechanical properties of heat-treated 7075 aluminum alloy components could lead to the development of lighter, stronger, and more durable materials for use in energy infrastructure, such as wind turbines, solar panels, and energy storage systems. The ability to improve the mechanical properties of additive manufactured components through heat treatment opens up new possibilities for the design and fabrication of complex, high-performance structures.
Despite the significant improvements, the researchers noted that residual insoluble Fe and Si compounds limited further mechanical property enhancements. Additionally, large pores densely distributed within the interlayer caused lower mechanical properties in the deposition direction compared to the cladding direction. These challenges present opportunities for future research and development in optimizing the additive manufacturing and heat treatment processes.
As the energy sector continues to evolve, the demand for advanced materials that can withstand extreme conditions and provide superior performance is on the rise. The research conducted by Yiqi Wang and his team at Jiangsu University of Technology represents a significant step forward in meeting these demands. By leveraging the potential of Wire Arc Additive Manufacturing and heat treatment, the energy sector can look forward to a future of innovative, high-performance materials that drive efficiency and sustainability.
In the words of Yiqi Wang, “This research not only advances our understanding of the microstructure and properties of heat-treated arc additively manufactured 7075 aluminum alloy components but also paves the way for their practical applications in the energy sector and other industries.” As the field continues to evolve, the insights gained from this study will undoubtedly shape future developments and inspire further innovation.