Purdue researchers develop ultrastrong aluminium alloys for Additive Manufacturing
July 9, 2024
Material engineers from Purdue University, West Lafayette, Indiana, USA, have created a patent-pending process to develop ultra-high-strength aluminium alloys with a plastic deformity that makes them suitable for Additive Manufacturing.
The project team – led by Haiyan Wang, the Basil S Turner Professor of Engineering, and Xinghang Zhang, School of Materials Professor – introduced cobalt, iron, nickel and titanium into aluminium via nanoscale, laminated, deformable intermetallics.
“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 said. “These alloys improve upon traditional ones that are either ultrastrong or highly deformable, but not both.”
Wang and Zhang disclosed the discovery to the Purdue Innovates Office of Technology Commercialization, which has applied for a US trademark.
Drawbacks of traditional aluminium alloys
Lightweight, high-strength aluminium alloys are used in industries from aerospace to automotive manufacturing. “However, most commercially available high-strength aluminium alloys cannot be used in Additive Manufacturing,” stated Anyu Shang, a Materials Engineering graduate student involved in the project. “They are highly susceptible to hot cracking, which creates defects that could lead to the deterioration of a metal alloy.”
A traditional method to alleviate hot cracking during the Additive Manufacturing process is the introduction of particles that strengthen aluminium alloys by impeding the movements of dislocations.
“But the highest strength these alloys achieve is in the range of 300 to 500 megapascals, which is much lower than what steels can achieve, typically 600 to 1,000 megapascals,” Wang said. “There has been limited success in producing high-strength aluminium alloys that also display beneficial large plastic deformability.”
The Purdue method and its validation
The Purdue researchers have produced intermetallics-strengthened aluminium alloys for AM by using several transition metals including cobalt, iron, nickel and titanium.
Shang explained that these metals have traditionally been avoided in the manufacture of aluminium alloys. “These intermetallics have crystal structures with low symmetry and are known to be brittle at room temperature,” he stated. “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.”
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, and thus introduce nanoscale intermetallics and their nanolaminates.”
During the course of the project, the research team has conducted macroscale compression tests, micropillar compression tests and post-deformation analysis on the Purdue-created aluminium alloys.
“During the macroscale tests, the alloys revealed a combination of prominent plastic deformability and high strength, more than 900 megapascals,” reported Shang. “The micropillar tests displayed significant back stress in all regions, and certain regions had flow stresses exceeding a gigapascal.”
He stated that post-deformation analyses revealed that, in addition to abundant dislocation activities in the aluminium alloy matrix, complex dislocation structures and stacking faults formed in monoclinic Al9Co2-type brittle intermetallics.
Industry partners interested in developing or commercialising this research are invited to contact Parag Vasekar, the Purdue Research Foundation’s Business Development and Licensing Manager, Physical Sciences.
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