When tiny metal particles fly at supersonic speeds and hit a surface, they can stick together and form strong bonds.
This process is used in industries like 3D printing and cold spray coating to build strong parts and coatings.
But scientists at Cornell University have just discovered that going too fast might actually make the bonds weaker.
In a recent study, researchers launched tiny aluminum particles—each only about 20 micrometers wide—at an aluminum surface.
The particles were fired at speeds as high as 1,337 meters per second (that’s over three times the speed of sound!). Using high-speed cameras, the team recorded how the particles stuck to the surface.
They found something surprising.
As the particle speed increased, the bonding strength also increased—up to a point. But once the speed passed 1,060 meters per second, the bond strength began to drop. At the highest speed tested (1,337 m/s), the particles barely stuck at all.
Professor Mostafa Hassani, who led the research, said, “We thought faster speeds would always mean better bonding. But we found that after a certain point, going faster actually made the bond worse.”
Why?
The team discovered that at extremely high speeds, the surface and the particles can’t absorb all the impact energy through bending or shaping. Instead, the energy turns into something called elastic strain. This causes the particles to bounce back—or “snap” off the surface—weakening the bond.
Lead author Qi Tang explained that this finding helps us understand why some high-speed industrial processes don’t always work as expected. For example, very fast particles can damage or melt the surface, or even knock off particles that had already bonded.
The good news is that this research could help improve how we make strong, long-lasting metal parts. By finding the perfect speed for bonding, companies can avoid waste, reduce damage, and create better products.
Even though this study looked only at aluminum, the scientists believe the same rules apply to many other metals and alloys. Future studies will explore different particle sizes and how to make the surface more bond-friendly.
This discovery proves that in materials science, sometimes slowing down just a little makes all the difference.
