Plastic Deformation Recovery in Freestanding Nanocrystalline Aluminum and Gold Thin Films
Jagannathan Rajagopalan,
Jong H. Han,
M. Taher A. Saif*
In nanocrystalline metals, lack of intragranular dislocation
sources leads to plastic deformation mechanisms that substantially
differ from those in coarse-grained metals. However, irrespective
of grain size, plastic deformation is considered irrecoverable.
We show experimentally that plastically deformed nanocrystalline
aluminum and gold films with grain sizes of 65 nanometers and
50 nanometers, respectively, recovered a substantial fraction
(50 to 100%) of plastic strain after unloading. This recovery
was time dependent and was expedited at higher temperatures.
Furthermore, the stress-strain characteristics during the next
loading remained almost unchanged when strain recovery was complete.
These observations in two dissimilar face-centered cubic metals
suggest that strain recovery might be characteristic of other
metals with similar grain sizes and crystalline packing.
* To whom correspondence should be addressed. E-mail: saif{at}uiuc.edu
