Frames from a dark-field TEM video of nanocrystalline nickel under strain show rapid aggregation of a group of grains.
A nanocrystalline metal is one whose average grain size is measured in billionths of a meter, much smaller than in most ordinary metals. As the grain size of a metal shrinks, it can become many times stronger, but it also usually loses ductility. To take advantage of increasing strength with decreasing grain size, researchers must first understand a fundamental problem: by what processes do nanosized crystals of metal stretch, bend, or otherwise deform under strain?
A team of researchers headed by Scott X. Mao of the Mechanical Engineering Department of the University of Pittsburgh, working at the National Center for Electron Microscopy (NCEM) at the Department of Energy’s Lawrence Berkeley National Laboratory, and using high-quality samples of nickel prepared at DOE’s Sandia National Laboratories, has now identified a prominent way in which nanocrystalline metals deform. The researchers report their findings in the July 30, 2004 issue of Science.
Ordinary coarse-grained metals deform when parts of a grain slip past one another as extra planes of atoms, called dislocations, move through the material. The process has been compared to moving a rug by flapping one end of it to create a wave, causing the rug to inch along bit by bit. But the trick won’t work if the rug is too short; likewise, if the dimensions of the crystal grains are too small, dislocations can’t be created or glide through the grain to allow deformation.
Paul Preuss | EurekAlert!
Dresdner scientists print tomorrow’s world
08.02.2017 | Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS
New technology for mass-production of complex molded composite components
23.01.2017 | Evonik Industries AG
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
17.02.2017 | Medical Engineering
17.02.2017 | Medical Engineering
17.02.2017 | Health and Medicine