Microscope view of
copper (top) welded to titanium (bottom) using a new technique developed
at The Ohio State
University. Image by Glenn Daehn, courtesy of The Ohio State University.
(October 29, 2015) New
welding technique can weld “un-weldable” metals
Engineers at The Ohio State University have developed a new
welding technique that consumes 80 percent less energy than a common welding
technique, yet creates bonds that are 50 percent stronger.
The new technique could have a huge impact on the auto
industry, which is poised to offer new cars which combine traditional heavy
steel parts with lighter, alternative metals to reduce vehicle weight.
Despite recent advances in materials design, alternative
metals still pose a challenge to manufacturers in practice. Many are considered
un-weldable by traditional means, in part because high heat and
re-solidification weaken them, said Glenn Daehn, professor of materials science
and engineering at Ohio State, who helped develop the new technique.
Microscope view of
steel (top) welded to aluminum alloy (bottom) using a new technique
invented at The
Ohio State University. Image by Glenn Daehn, courtesy of The Ohio State
University.
“Materials have gotten stronger, but welds haven’t. We can
design metals with intricate microstructures, but we destroy the microstructure
when we weld,” he said.
“With our method, materials are shaped and bonded together
at the same time, and they actually get stronger.”
Daehn explained the new process in a keynote address at the
Materials Science & Technology 2015 meeting recently in Columbus.
A diagram showing
vaporized foil actuator welding, a technique developed at The
Ohio State
University. Image by Glenn Daehn, courtesy of The Ohio State University.
In a common technique called resistance spot welding,
manufacturers pass 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 (VFA) 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.