The Welds Which Bind

Ohio State University engineers, including professor of materials science and engineering Glenn Daehn, have developed a new kind of welding that consumes 80 percent less energy, but creates bonds 50 percent stronger than traditional methods. The technique could be a revolution in the auto industry, where bonding heavier and lighter weight metals would allow manufacturers to create vehicles that weigh significantly less.

Traditional spot welding passes a high electrical current through pieces of metal, so that the metals’ natural electrical resistance generates heat that partially melts them together and forms a weld. The drawbacks: generating high currents consumes a lot of energy, and the melted portions of metal are never as strong afterward as they were before.

Over the last decade, Daehn and his team have been trying to find ways around those problems. They’ve amassed more than half a dozen patents on a system called vaporized foil actuator welding.
In VFA, a high-voltage capacitor bank creates a very short electrical pulse inside a thin piece of aluminum foil. Within microseconds (millionths of a second), the foil vaporizes, and a burst of hot gas pushes two pieces of metal together at speeds approaching thousands of miles per hour. The metals don’t melt, so there’s no seam of weakened metal between them. The impact directly bonds the atoms of one metal to atoms of the other.

So far, the engineers have successfully bonded different combinations of copper, aluminum, magnesium, iron, nickel and titanium. They have created strong bonds between commercial steel and aluminum alloys—a feat which is impossible normally. Also, high-strength steel and aluminum join together with weld regions that are stronger than the base metals.