In a groundbreaking development for the aerospace and automotive industries, researchers have successfully fabricated a novel multi-alloy aluminum-based functional gradient material (AFGM) using a solid-state additive manufacturing technique. This innovation promises to revolutionize the way dissimilar aluminum alloys are integrated, potentially eliminating weak joints and enhancing the durability of critical structures.
The study, led by Rajasanthosh Kumar Tulala from the Department of Mechanical Engineering at Puducherry Technological University in India, focuses on the fabrication and evaluation of a five-layer AFGM. By strategically stacking AA7075, AA2024, AA6061, AA5083, and AA1100 alloys in a tensile-strength-guided sequence, the team created a continuous gradient of strength-to-ductility within a single structure. This approach leverages the unique capabilities of Friction Stir Additive Manufacturing (FSAM), a solid-state additive manufacturing technique, to produce defect-free interfaces and refined grain structures.
“Traditional methods of joining dissimilar aluminum alloys, such as welding or riveting, often introduce weak points and reduce the overall durability of the structure,” explains Tulala. “Our research demonstrates that by using FSAM and a strength-based alloy stacking strategy, we can fabricate anisotropic and structurally robust AFGMs that outperform conventional assemblies.”
The team produced multilayer builds using two different tool rotational speeds: 600 and 700 RPM. Microstructural analysis revealed that the lower rotational speed (600 RPM) resulted in refined grains and defect-free interfaces, while the higher speed (700 RPM) induced coarser grains with localized interfacial softening. Energy Dispersive X-ray (EDX) analysis confirmed the enrichment of strengthening elements (Cu, Zn, and Mg) in the upper layers, correlating with the observed hardness distribution.
Mechanical testing showed that samples produced at 600 RPM achieved the highest tensile strength, with ultimate tensile strength (UTS) of 410 MPa and yield strength (YS) of 220 MPa. In contrast, the transverse direction (TD) samples of 700 RPM exhibited maximum ductility, with an elongation of 29.5%. All samples maintained a UTS to YS ratio greater than 1.5, confirming ductile behavior with strain hardening.
The implications of this research are significant for the energy sector, particularly in aerospace and automotive applications. By replacing multi-alloy assemblies with a single graded material, manufacturers can reduce joining defects and enhance the overall performance and durability of their products. This innovation could lead to lighter, stronger, and more efficient structures, ultimately reducing fuel consumption and emissions.
“This research opens up new possibilities for the design and fabrication of advanced materials tailored to specific applications,” says Tulala. “The ability to create a continuous gradient of properties within a single structure offers unprecedented flexibility and performance advantages.”
Published in the journal Materials Research Express, which translates to “Materials Research Expressions” in English, this study highlights the potential of FSAM in producing high-performance AFGMs. As the demand for lightweight and durable materials continues to grow, this research paves the way for future developments in the field of additive manufacturing and materials science.
The findings of this study not only advance our understanding of the microstructure-mechanical property correlations in AFGMs but also provide a scalable pathway to replace conventional multi-alloy assemblies with a single, high-performance material. This innovation could have far-reaching implications for various industries, including aerospace, automotive, and energy, driving the next generation of advanced materials and manufacturing technologies.