Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Twinning phenomenon found in nanocrystalline aluminum

31.07.2003


Using a powerful electron microscope to view atomic-level details, Johns Hopkins researchers have discovered a "twinning" phenomenon in a nanocrystalline form of aluminum that was plastically deformed during lab experiments. The finding will help scientists better predict the mechanical behavior and reliability of new types of specially fabricated metals. The research results, an important advance in the understanding of metallic nanomaterials, were published in a recent issue of the journal Science.



At the microscopic level, most metals are made up of tiny crystallites, or grains. Through careful lab processing, however, scientists in recent years have begun to produced nanocrystalline forms of metals in which the individual grains are much smaller. These nanocrystalline forms are prized because they are much stronger and harder than their commercial-grade counterparts. Although they are costly to produce in large quantities, these nanomaterials can be used to make critical components for tiny machines called microelectromechanical systems, often referred to as MEMS, or even smaller nanoelectromechanical systems, NEMS.

But before they build devices with nanomaterials, engineers need a better idea of how the metals will behave. For example, under what conditions will they bend or break? To find out what happens to these new metals under stress at the atomic level, Johns Hopkins researchers, led by Mingwei Chen, conducted experiments on a thin film of nanocrystalline aluminum. Grains in this form of aluminum are 1,000th the size of the grains in commercial aluminum.


Chen and his colleagues employed two methods to deform the nanomaterial or cause it to change shape. The researchers used a diamond-tipped indenter to punch a tiny hole in one piece of film and subjected another piece to grinding in a mortar. The ultra-thin edge of the punched hole and tiny fragments from the grinding were then examined under a transmission electron microscope, which allowed the researchers to study what had happened to the material at the atomic level. The researchers saw that some rows of atoms had shifted into a zig-zag pattern, resembling the bellows of an accordion. This type of realignment, called deformation twinning, helps explain how the nanomaterial, which is stronger and harder than conventional materials, deforms when subjected to high loads.

"This was an important finding because deformation twinning does not occur in traditional coarse-grain forms of aluminum," said Chen, an associate research scientist in the Department of Mechanical Engineering in the university’s Whiting School of Engineering. "Using computer simulations, other researchers had predicted that deformation twinning would be seen in nanocrystalline aluminum. We were the first to confirm this through laboratory experiments."

By seeing how the nanomaterial deforms at the atomic level, researchers are gaining a better understanding of why these metals do not bend or break as easily as commercial metals do. "This discovery will help us build new models to predict how reliably new nanoscale materials will perform when subjected to mechanical forces in real-world devices," said Kevin J. Hemker, a professor of mechanical engineering and a co-author of the Science paper. "Before we can construct these models, we need to improve our fundamental understanding of what happens to nanomaterials at the atomic level. This is a key piece of the puzzle."

The nanocrystalline aluminum used in the experiments was fabricated in the laboratory of En Ma, a professor in the Department of Materials Science and Engineering and another co-author of the research paper. "This discovery nails down one deformation process that occurs in nanocrystalline metals," Ma said. "This is the first time a new mechanism, which is unique to nanostructures and improbable in normal aluminum, has been conclusively demonstrated."

Other co-authors of the paper were Hongwei Sheng, an associate research scientist in the Department of Materials Science and Engineering; Yinmin Wang, a graduate student in the Department of Materials Science and Engineering; and Xuemei Cheng, a graduate student in the Department of Physics and Astronomy.

Phil Sneiderman | EurekAlert!
Further information:
http://www.me.jhu.edu

More articles from Physics and Astronomy:

nachricht Applicability of dynamic facilitation theory to binary hard disk systems
08.12.2016 | Nagoya Institute of Technology

nachricht Will Earth still exist 5 billion years from now?
08.12.2016 | KU Leuven

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Closing the carbon loop

08.12.2016 | Life Sciences

Applicability of dynamic facilitation theory to binary hard disk systems

08.12.2016 | Physics and Astronomy

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>