Making Future Cars Stronger, Using Less Energy: New Technique Creates Stronger Metals

Engineers have devised a new welding technique that uses 80 percent less energy than typical welding techniques, and creates bonds that are 50 percent stronger. This could be a major breakthrough for the auto industry, where cars can be built stronger using light steel parts, according to a study at 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," said Glenn Daehn, who helped develop the technique, in a news release "With our method, materials are shaped and bonded together at the same time, and they actually get stronger."

Many metals are considered "unweldable," since high heat and re-solidification weakens them, according to Daehn, who is a professor of materials science and engineering at Ohio State.

In one typical technique, known as spot welding, high volts of electric current are passed through various pieces of metal that are melted together, forming the weld. However, this technique consumes great amounts energy and the melted portions of the metals being used are not as strong as they were prior to being welded.

Daehn and his team created a new system called vaporized foil actuator (VFA) welding. In this technique, a high-voltage capacitor bank generates a short electric pulse inside a thin piece of aluminum foil. In a matter of microseconds, the foil become a vapor and a burst of hot gas pushes the two pieces of metal together at a rate of thousands of miles per hour, according to the researchers.

The pieces of metal do not experience any form of melting, thus there are no seams of weak metal between the two pieces. The impact directly bonds the atoms of one metal to atoms of the other metal. Less energy is used in this technique, since there is a shorted electric pulse. The energy used to vaporize the foil is less than what is required to melt metal parts, according to the researchers.

The engineers have successfully bonded various combinations of magnesium, iron, copper, aluminum, nickel and titanium. They even created strong bonds between commercial steel and aluminum alloys, which is often impossible. The high strength of steel and aluminum put together with welded regions were actual stronger than the base metals themselves.

This new technique grants the power to shape metal parts and weld them together more efficiently. The team of engineers are planning to further develop the technology, so it can be a licensed and be a commercial service to various industries.

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