WASHINGTON, Dec. 21 (Xinhua) -- Scientists from the California Institute of Technology have created a range of structural metallic-glass composites, based in titanium, that are lighter and less expensive than any the group had previously created, while still maintaining their toughness and ductility -- the ability to be deformed without breaking.

    A paper describing these breakthrough metallic-glass alloys was published in the latest online issue of the Proceedings of the National Academy of Sciences (PNAS).

    Earlier this year, the same Caltech group had published a paper in the journal Nature, describing new strategies for creating the liquid-metal composites.

    However, there were shortcomings to the alloys presented in Nature. Because they were created for use in the aerospace industry -- among other structural applications -- they needed to have very low densities. Ideally, the alloys would have had densities in or around those of crystalline titanium alloys, whichfall between 4.5 and 5 grams per cubic centimeter (g/cc). The original alloys, made predominantly of zirconium, fell between 5.6and 6.4 g/cc, putting them "in a no-man's-land of densities for aerospace structures."

    So the researchers began tweaking the components in their composites, eventually coming up with a group of alloys with a high percentage of titanium, but which maintained the properties of the previously created zirconium alloys.

    The scientists finally created "alloys with unrivaled strength and toughness." "They are among the toughest engineering materials that currently exist," lead researcher Douglas Hofmann noted.

    Despite being based in titanium, these new alloys exhibit the same impressive properties as the zirconium alloys. They are still tough -- in other words, they resist cracking -- and they are still ductile. "In fact, they are even more ductile than the alloys we'd created in the past," says Hofmann.

    This decrease in density also resulted in a reduction in cost, adds Hofmann, since zirconium is a more expensive metal than is titanium.