Makes the Dents Vanish -- COMPAMED Trade Fair

Makes the Dents Vanish

Photo: Crinkly tin foil

Normally, when a piece of metal is bent, the change in shape becomes permanent. But, when heat is added to bent metal films having the right microstructure, the researchers found, the films return to their original shapes. The higher the temperature, the sooner the metal films revert. "It’s as though the metal has a memory of where it came from," said Taher A. Saif, a professor of mechanical science and engineering at Illinois.


"We found that the type of metal doesn’t matter, said Saif. "What matters is the size of the grains in the metal’s crystalline microstructure, and a distribution in the size." Grain sizes are typically one-third to one-half the thickness of a metal film. Raising the temperature by about 50 degrees Celsius causes the grains to grow larger.

If the grains are uniformly too small, the metal will be brittle and break while being bent. If the grains are uniformly too large, the metal will bend, but then stay in that position. To return to the initial shape, what’s needed is a balance between brittleness and malleability.


Controlling the crystalline microstructure of thin films also could reduce energy loss in oscillators and resonators used in electronic circuits, Saif said. Oscillators and resonators are found in products ranging from air bag sensors and camcorders to digital projectors and global positioning systems.; Source: University of Illinois at Urbana-Champaign