Glass that's Stronger than Steel

WASHINGTON: Scientists have come up with a new type of glass from opaque titanium and zirconium, which is harder, tougher and weighs less than stainless steel. According to a report in Discovery News, the glass has been developed by scientists at the Lawrence Berkeley National Laboratory, California, US. The experts who developed and tested the opaque glass hope it could one day replace steel and aluminum in a variety of products, from golf clubs to airplanes.

“The problem with most (types of) glass is that they have very bad fatigue resistance,” meaning they break easily, said Maximilien Launey, a scientist at the Lawrence Berkeley National Laboratory. “What we’ve done is introduce a second phase that is able to improve the fatigue resistance. Now, it’s as good as other high-strength alloys like steel,” he added.

To create the tough, metallic glass, the scientists first heat an alloy of half titanium and half zirconium to 800°C until melt. The liquid metal is allowed to cool slowly for a minute or two, and then cooled very rapidly after that.
By cooling slowly and then quickly, the scientists allowed tiny Christmas tree-like crystalline structures to grow through the metal. Rapidly cooling the rest of the metal maintains the glassy atomic structure.

The crystalline structures stop any cracks that from moving more than two to five microns in length. The glass gives the material its strength, while the Christmas tree-structures give it toughness. In subsequent stress tests, the 1 to 10-centimeter pieces of glass were dramatically tougher than any previous metallic glass, a full order of magnitude more resistant to breaking and stronger than steel.

Since the alloy is titanium and zirconium instead of steel, it weighs significantly less than steel. It also melts at much lower temperatures than steel, making it easier and faster to produce. It also melts at much lower temperatures than steel, making it easier and faster to produce. “We could make an airplane out of metallic glass,” said Launey.