Rongmei niu's blog

1. Strain hardening and softening in nanotwinned Cu:

Nanotwinned Cu foils with about 99% coherent twin boundaries (TBs) among all the boundaries were made. These coherent

TBs, with an average spacing of 25 nm, were engineered approximately parallel to foil surfaces. Low plane-strain deformation

enhances the hardness by refining microstructure and introducing dislocations. High plane-strain deformation results in crystallographic

lattice rotation and reaction between dislocations and coherent TBs, and induces incoherent TBs, thus twin coarsening and

Postdoctoral
Research Associate Position

The
National High Magnetic Field Laboratory (NHMFL) in Tallahassee, FL is seeking a
Postdoctoral Research Associate to work on nanostructured permanent magnets.  Preference will be given to candidates who
have a strong commitment to research and development, and can actively contribute
to the programs within the NHMFL.

For the polymer-supported metal thin films that are finding increasing applications, the critical strain to nucleate microcracks ( εc ) should be more meaningful than the generally measured rupture strain. In this paper, we develop both electrical resistance method and microcrack analyzing method to determine εc of polymer-supported Cu films simply but precisely. Significant thickness dependence has been clearly revealed for εc of the polymer-supported Cu films, i.e., thinner is the film lower is εc . This dependence is suggested to cause by the constraint effect of refining grain size on the dislocation movability.