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 the 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 a stronger bond.
With a traditional option like resistance spot welding, manufacturers pass a high electrical current through pieces of metal. The metals’ natural electrical resistance generates heat that partially melts them together and forms a weld. Generating high currents, however, consumes a lot of energy, and the melted portions of metal are weakened.
The Ohio State researchers' vaporized foil actuator (VFA) welding method uses a high-voltage capacitor bank to create 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 speeds approaching thousands of miles per hour.
Because the pieces do not melt, there is no seam of weakened metal between them. Instead, the impact directly bonds the atoms of one metal to atoms of the other. The shortened pulse also uses less energy.
The researchers have created strong bonds between commercial steel and aluminum alloys. The technique is powerful enough to shape metal parts at the same time it welds them together, saving manufacturers a step.
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