New Model Shows How Metallic Alloys Behave at the Nanoscale

When it comes to metals, strength, durability, reliability, and resistance to wear are some key properties engineers consider. Yet, the processes that influence those properties often occur at scales too small to see. 

Research by Northwestern Engineering's Fadi Abdeljawad sheds light on those hidden processes. It offers a novel way to understand and ultimately design advanced metallic materials by providing a framework for predicting how complex combinations of elements behave inside metals. This advance could help accelerate the development of materials for aerospace, energy, transportation, and other critical technologies.

“The goal is to understand how materials behave at near-atomic-scale resolution,” Abdeljawad said. “The properties of these materials are directly related to how their atoms are arranged.”

Abdeljawad is an associate professor of materials science and engineering at the McCormick School of Engineering. He was part of a team that reported this work in the paper “Grain Boundary Segregation and Solute Drag in Multicomponent Alloys,” published earlier this year in Nature Communications.

Most metallic materials are not single, uniform structures. Instead, they are made up of countless microscopic crystals packed together. The boundaries where those crystals meet—known as grain boundaries—play an outsized role in determining how a material performs. 

For decades, scientists have known that grain boundaries influence everything from mechanical strength to thermal performance. What has proven more difficult is understanding exactly how chemistry affects those interfaces in complex metallic alloys used in real-world applications.

“Structural materials are typically made by combining multiple chemical elements,” Abdeljawad said. “Historically, computational and engineering models relied on simplifying assumptions limiting their predictive power. We're moving beyond these assumptions.”

In the study, Abdeljawad and his group developed a theoretical and computational framework that captures how multiple alloying elements interact simultaneously at grain boundaries. Their work focuses on grain-boundary segregation—the tendency of some elements to concentrate at those interfaces—and a related phenomenon known as solute drag, which can influence how grain boundaries move during materials synthesis and processing. The findings reveal that the interactions among multiple alloying elements can be far more complex than previously understood.

While the work is fundamentally focused on atomic-scale behavior, its implications are easy to spot.

Engineers often develop materials through extensive testing, adjusting compositions and processing conditions until they achieve the desired result. Abdeljawad hopes research like this can make that process far more predictable.

“The ultimate goal is to move away from costly trial-and-error materials design and toward a more physics-based approach that allows engineers to design materials with confidence,” he said.

The research also challenges a long-standing assumption in materials science. Grain boundaries have traditionally been viewed as defects—features that are detrimental to materials properties. Abdeljawad's work suggests they can instead become valuable tools for materials design.

“What we're hoping to show is that by carefully controlling the chemistry of these interfaces, we can stop thinking of them as defects and start treating them as design tools,” he said.