杏吧原创

HOPES of making harder metals built from nanocrystals have been dashed.

Metals consist of a jumble of micrometre-sized crystals or
grains. Metallurgists thought they could make them harder by shrinking these
grains鈥攁 process known as the Hall-Petch effect.

But in computer simulations, Jakob Schi酶tz and his colleagues at the
Technical University of Denmark in Lyngby have shown that copper grains about
five nanometres across are softer than their bigger brothers. 鈥淭his limits the
eventual strength of these metals,鈥� says Schi酶tz.

The team suggests in Nature (vol 381, p 561) that while the softness
of micrometre-sized grains arises because they deform under stress, the softness
of smaller grains is a result of their sliding past each other.