11/23/2010

Strong yet so ductile

Anne M Stark, LLNL, (925) 422-9799, stark8@llnl.gov




Ultrahigh strength materials such as nanocrystalline solids are notoriously known for the dismally-low ductility due to their lack of effective strain hardening mechanisms. This trait severely curbs their practical utilities.

By using in-situ synchrotron X-ray diffraction and high-resolution electron microscopy, Yinmin Wang of the Lab's Condensed Matter and Materials Division and his colleagues from Ames Laboratory and Argonne National Laboratory discovered that efficient defect storage and strain hardening become possible when planar-defect-related deformation mechanism (such as mechanical twinning) is introduced in the dislocation-resistant nanograins (less than 20 nanometers). As a result, large tensile-ductility can be achieved in these love-hate materials.

The finding further reveals distinctive deformation mechanisms in different crystallographic nanocrystalline materials, and has general implications in helping design ultratough nanostructured materials (i.e., materials with both high strength and large ductility) for applications in weight-saving, shape-forming, protection-coating, and MEMS.

"This finding shows that we can 'toughen' nanostructured materials and improve their utility," Wang said. 

The research appears in the Nov. 17 edition of Physical Review Letters.

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