RT Journal Article
SR Electronic
T1 Enhanced thermal stability of nanograined metals below a critical grain size
JF Science
JO Science
FD American Association for the Advancement of Science
SP 526
OP 530
DO 10.1126/science.aar6941
VO 360
IS 6388
A1 Zhou, X.
A1 Li, X. Y.
A1 Lu, K.
YR 2018
UL http://science.sciencemag.org/content/360/6388/526.abstract
AB Synthesizing metals with extremely small (nanoscale) grain sizes makes for much stronger materials. However, very small–grained materials start to coarsen at relatively low temperatures, wiping out their most desirable properties. Zhou et al. discovered a way to avoid this problem by mechanically grinding copper and nickel at liquid nitrogen temperatures. The processing method creates low-angle grain boundaries between the nanograins, which promotes thermal stability.Science, this issue p. 526The limitation of nanograined materials is their strong tendency to coarsen at elevated temperatures. As grain size decreases into the nanoscale, grain coarsening occurs at much lower temperatures, as low as ambient temperatures for some metals. We discovered that nanometer-sized grains in pure copper and nickel produced from plastic deformation at low temperatures exhibit notable thermal stability below a critical grain size. The instability temperature rises substantially at smaller grain sizes, and the nanograins remain stable even above the recrystallization temperatures of coarse grains. The inherent thermal stability of nanograins originates from an autonomous grain boundary evolution to low-energy states due to activation of partial dislocations in plastic deformation.