Material engineers at Purdue University have pioneered a method to produce ultrahigh-strength aluminium alloys tailored for additive manufacturing (AM). Leveraging the inherent plastic deformability of these alloys, the patented process marks a significant advancement poised to transform industries dependent on lightweight materials with exceptional strength. Researchers anticipate this innovation will redefine the capabilities of high-performance manufacturing.
Image source - Purdue University, Anyu Shang
Purdue researchers have developed intermetallic-strengthened aluminium alloys by integrating transition metals such as cobalt, iron, nickel, and titanium. Traditionally, these metals have been excluded from aluminium alloy manufacturing due to their tendency to become brittle at room temperature. The research team thoroughly validated their method, including macroscale compression tests, micropillar compression tests, and post-deformation analyses on the newly developed aluminium alloys.
The research team
Haiyan Wang, the Basil S. Turner Professor of Engineering, and Xinghang Zhang, a professor in Purdue's School of Materials Engineering, lead the pioneering research team. They collaborate with Anyu Shang, a graduate student in materials engineering. Together, they developed a method incorporating transition metals like cobalt, iron, nickel, and titanium into aluminium using nanoscale laminated deformable intermetallics. This innovative approach promises to enhance the properties of aluminium alloys significantly.
"These intermetallics have crystal structures with low symmetry and are known to be brittle at room temperature. But our method forms the transitional metal elements into colonies of nanoscale, intermetallics lamellae that aggregate into fine rosettes. The nanolaminated rosettes can largely suppress the brittle nature of intermetallics," said Anyu Shang.
Wang added, "The heterogeneous microstructures contain hard nanoscale intermetallics and a coarse-grain aluminium matrix, which induces significant back stress that can improve the work hardening ability of metallic materials. Additive manufacturing using a laser can enable rapid melting and quenching, introducing nanoscale intermetallics and their nanolaminates."
Safeguarding the invention
Wang and Zhang have shared their innovation with Purdue's Innovates Office of Technology Commercialisation, which has initiated a patent application with the U.S. Patent and Trademark Office to safeguard their intellectual property. Their research, featured in the peer-reviewed journal Nature Communications, received funding from the National Science Foundation and the U.S. Office of Naval Research.
“During the macroscale tests, the alloys revealed a combination of prominent plastic deformability and high strength, more than 900 megapascals. The micropillar tests displayed significant back stress in all regions, and certain regions had flow stresses exceeding a gigapascal. Post-deformation analyses revealed that, in addition to abundant dislocation activities in the aluminum alloy matrix, complex dislocation structures and stacking faults formed in monoclinic Al9Co2-type brittle intermetallics,” added Shang.
“Our work shows that the proper introduction of heterogenous microstructures and nanoscale medium-entropy intermetallics offers an alternative solution to design ultrastrong, deformable aluminium alloys via additive manufacturing,” Zhang stated.
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