From Scientific American:
A metal alloy masquerading as a glass is the first material to be fabricated that is as strong and as tough as the toughest steel. The feat could eventually see such materials replace steel in buildings, cars or bridges.
The terms ‘strength’ and ‘toughness’ may be used almost interchangeably in everyday life, but until now, no materials have been found that display both these characteristics. Some materials, such as glass, are strong — that is, they are scratch-resistant and it is difficult to permanently bend them out of shape when you place a heavy load on them — but they also tend to be brittle. Others, such as metal, are tough — that is, they are more difficult to shatter — but they are generally more malleable.
“The challenge has always been to achieve both high strength and toughness,” says Marios Demetriou, a materials scientist at the California Institute of Technology in Pasadena. “But until now we have always had to compromise between the two.”