Ateam of engineers from The Ohio State University (OSU) has developed a new welding technique that could boost the auto industry’s efforts to offer vehicles that weigh less and are more fuel efficient.
The Department of Energy (DOE) is investing $2.7 million to further develop vaporizing foil actuator welding (VFAW) as a viable technology for creating multi-material, lightweight vehicles, a technology developed by OSU Professor of Materials Science and Engineering Glenn Daehn and colleagues.
In VFAW, a high-voltage capacitor bank creates a very short electrical pulse inside a thin piece of aluminum foil. Within microseconds, the foil vaporizes, and a burst of hot gas pushes two pieces of metal together at thousands of miles per hour.
The pieces don’t melt, so there’s no seam of weakened metal between them. Instead, the impact directly bonds the atoms of one metal to atoms of the other. This addresses one of the biggest issues in joining advanced and dissimilar metals without producing joints that are much weaker than the base metals.
“VFAW consumes less than one-fifth of the energy than a common welding technique,” Daehn says, “yet creates bonds that are 50% stronger.”
Along with Daehn, Materials Science and Engineering Research Scientist Anupam Vivek is co-principal investigator on the DOE-funded project which will span four years.
“Widely disparate combinations of metals can be welded with nearly 100% joint efficiency by VFAW,” Vivek explains. “This enables introduction of high strength-to-weight ratio materials such as aluminum and magnesium into the body of the car, which has traditionally been made of steel.”
By effectively slamming disparate metals against each other at extremely high velocities, OSU researchers have joined steel to aluminum, high-strength steel to aluminum, titanium to copper, and copper to tungsten. The collision-joining processes creates a wavy microscopic interface between surfaces resembling ocean waves. The interlocking waves create a solid-state bond between surfaces that passes the standard weld-strength test – when mechanically peeled apart, the parts fail in the base metals, not in the joint.
In 2013, Daehn’s team received a $600,000 DOE award for “Breakthrough Technologies for Dissimilar Material Joining.” The results from that project and related works have been published extensively. Additionally, grants from the university, State of Ohio, and the National Science Foundation’s I-Corps program have funded efforts to advance the technology toward commercial use.
The researchers anticipate automakers will start using VFAW for full-scale production within the next several years. Project partners include Alcoa, Ashland Chemical, Pacific Northwest National Laboratory, Coldwater Machine Co., OSU’s Center for Design and Manufacturing Excellence, Fontana Corrosion Center, and Magna International subsidiary Cosma.
Coldwater Machine will work with Ohio State to create a manufacture-ready system for VFAW, including development of two units in the fall of 2017. Other collaborators include Honda and its supplier Jefferson Industries, which are working to bring the technology into production as a head unit for robotic implementation, while Ashland will validate corrosion control methodologies.
The Ohio State University, Impulse Manufacturing Laboratory