February 28, 2013
Temperature Determines Whether Glass Will Bend Or Break
Lee Rannals for redOrbit.com — Your Universe Online
Researchers have found a way to determine whether glass will be brittle, or will have the ability to bend without breaking.
The team wrote in the journal Nature Communications about how they've identified a temperature that allows you to determine whether you will be forming a brittle piece of glass, or ductile, which refers to a piece of glass' toughness.
There is a temperature at which glass can become too viscous for reconfiguration, and then freezes. This temperature is known as the glass transition temperature.
Researchers performed experiments with three representatives in bulk metallic glasses (BMGs), which are metal alloys that can be extremely pliable and also strong. For each distinct alloy, there is a critical temperature that determines the brittleness or plasticity of the glass, which is known as critical fictive temperature (CFT).
They said it is possible to categorize glasses in two groups: either those that are brittle because in liquid form their CFT is above the glass transition temperature; or those that are ductile because in liquid form their CFT is below the glass transition temperature.
The team had originally believed a liquid's chemical composition would be able to determine whether a glass would be brittle or ductile. However, Jan Schroers, a professor of mechanical engineering and materials science at Yale, said this was not the case.
"We can make any glass theoretically ductile or brittle. And it is the critical fictive temperature which determines how experimentally difficult it is to make a ductile glass. That is the major contribution of this work," said Schroers.
Golden Kumar, a professor at Texas Tech University who was lead author of the paper, told redOrbit that they envision two important implications for their work.
"First, this will enhance our fundamental understanding of glasses and liquids. Second, it will bring some metallic glasses back in application market, which were discarded primarily because of their brittle nature," said Kumar. "We feel that the overall applications of metallic glasses will still be in small scale devices because of material cost and fabrication ease."
He also talked about what he saw as the most fascinating part of the team's research.
"The most fascinating part was to discover something which challenges the conventional belief. We always thought that glasses are brittle, metals are ductile, and metallic glasses are somewhat in between," he told redOrbit. "Now we know that all metallic glasses can deform plastically if prepared under appropriate conditions."