Purdue builds a cobalt aluminum alloy ten times stronger than structural steel

The material that refuses to bend or break

Jet engines need materials that survive enormous heat and force without warping, cracking, or slowly losing their shape. The strongest candidates usually fail on the same point: they are too brittle to deform safely. A team at Purdue University just changed that math for cobalt aluminum, an intermetallic compound with real potential in high performance turbines.

By rebuilding the material at the nanoscale, the researchers created a form of cobalt aluminum (CoAl) that is exceptionally strong and still able to deform at room temperature. The work, published in Science Advances, points toward a broader strategy for making notoriously brittle intermetallics usable in aerospace, energy, and defense.

Why intermetallics fracture

Intermetallics pack two or more metallic elements into a tightly ordered crystal. That order delivers remarkable strength, high melting points, and resistance to creep, the slow deformation that builds up under long term stress. The same order also stops the material from bending. Instead of yielding, many fracture, especially at room temperature.

CoAl is strong enough to be considered for turbine blades, but its brittleness makes it hard to shape and limits how much sudden stress it can take. "Bulk CoAl intermetallics are a high strength compound," said Xinghang Zhang, a professor in Purdue's School of Materials Engineering. "High strength, plastically deformable CoAl alloys could allow an engine or turbo to spin faster while sustaining higher centrifugal force."

Building defects on purpose

The team took an unusual path. Instead of avoiding imperfections, they built dislocations directly into CoAl as it formed during sputtering deposition. They also created a network of amorphous interfaces, thin boundaries where atoms lose their ordered arrangement.

Those flexible boundaries do more than separate layers. Under force, parts of the interfaces crystallize and help generate new dislocations, giving the surrounding CoAl more ways to absorb energy. "We designed the framework of amorphous interfaces, flexible boundaries in the materials for structural flexibility, which partially crystallize during deformation and promote the nucleation of the dislocations," Zhang said.

Stronger than steel, and still tough

The resulting nanolaminate reached a yield strength of 6 GPa, roughly six to ten times that of high strength structural steel. Yield strength is the stress a material endures before it starts to deform for good.

Despite that extreme strength, the material held 15% plastic strain under compression at room temperature. In plain terms, it could deform a lot before it fractured. "This combination of ultrahigh mechanical strength and outstanding plasticity makes the current CoAl nanolaminate system one of the best intermetallic systems reported to date," said Ke Xu, the study's first author.

What comes next

The bigger prize is a method, not just a material. If the same interface trick works across other brittle intermetallics, engineers could design a family of parts that stay strong without snapping. That matters for turbine blades, energy systems, and any component where failure is not an option.