Featured Research

from universities, journals, and other organizations

'A Touch Of Glass' In Metal, Settles Century-old Question

Date:
July 4, 2009
Source:
National Institute of Standards and Technology
Summary:
Scientists have found evidence of an important similarity between the behavior of polycrystalline materials -- like metals and ceramics -- and glasses, research that could lead to better predictions of how many valuable materials behave under stress.

Between a polycrystalline material's grains (saffron layers) exist disorderly areas called grain boundaries, the behavior of which has been difficult to understand. The green and blue objects in the boundary are string-like collections of atoms that NIST scientists have recently shown behave like glass-forming liquids, a similarity that should help scientists analyze a wide range of materials.
Credit: NIST

Better predictions of how many valuable materials behave under stress could be on the way from the National Institute of Standards and Technology (NIST), where scientists have recently found evidence of an important similarity between the behavior of polycrystalline materials—such as metals and ceramics—and glasses.

Most metals and ceramics used in manufacturing are polycrystals. The steel in a bridge girder is formed from innumerable tiny metal crystals that grew together in a patchwork as the molten steel cooled and solidified. Each crystal, or “grain,” is highly ordered on the inside, but in the thin boundaries it shares with the grains around it, the molecules are quite disorderly. Because grain boundaries profoundly affect the mechanical and electrical properties of polycrystalline materials, engineers would like a better understanding of grain boundaries’ formation and behavior. Unfortunately, grain boundary formation in most technically useful alloys has eluded efforts to observe it for a century.

“You’d like to have simple engineering rules regarding how a material’s going to break,” says NIST materials scientist Jack Douglas. “For example, corrosion typically travels along grain boundaries, so polycrystals usually fracture along them. But metals melt and deform at very high temperatures, so observing them under those conditions is a challenge.”

While some scientists had speculated that the molecules in grain boundaries behave similarly to the way molecules do in glass-forming liquids, whose properties are well understood, none had found conclusive evidence to back up such a claim. That started to change when NIST theorist James Warren saw a conference presentation by the University of Alberta’s Hao Zhang concerning some odd “strings” of atoms in his simulation of grain boundary motion using a simulation technique called molecular dynamics. The collective atomic behavior observed in grain boundaries reminded the team of prior findings made at NIST about glass-forming liquids, whose atoms also form strings.

Subsequently, the team showed that the strings of atoms arising in grain boundaries are strikingly similar in form, distribution and temperature dependence to the string-like collective atomic motions generally found in glass-forming liquids—and that properties for both types of substances change with temperature in virtually the same way. “This work represents a paradigm shift in our understanding of grain boundaries,” Douglas says. “All the important qualities relating to atomic motion in both of these types of materials—the development of these string-like atomic motions, or the amplitude at which their atoms rattle—are strikingly similar. For all intents and purposes, grain boundaries are a type of glass.”

Douglas says the findings could permit substantial progress in predicting the failure of many materials important in construction and manufacturing and could improve our understanding of how crystals form boundaries with one another.


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Zhang et al. Grain boundaries exhibit the dynamics of glass-forming liquids. Proceedings of the National Academy of Sciences, 2009; 106 (19): 7735 DOI: 10.1073/pnas.0900227106

Cite This Page:

National Institute of Standards and Technology. "'A Touch Of Glass' In Metal, Settles Century-old Question." ScienceDaily. ScienceDaily, 4 July 2009. <www.sciencedaily.com/releases/2009/06/090617123435.htm>.
National Institute of Standards and Technology. (2009, July 4). 'A Touch Of Glass' In Metal, Settles Century-old Question. ScienceDaily. Retrieved April 24, 2014 from www.sciencedaily.com/releases/2009/06/090617123435.htm
National Institute of Standards and Technology. "'A Touch Of Glass' In Metal, Settles Century-old Question." ScienceDaily. www.sciencedaily.com/releases/2009/06/090617123435.htm (accessed April 24, 2014).

Share This



More Matter & Energy News

Thursday, April 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Obama Plays Soccer With Japanese Robot

Raw: Obama Plays Soccer With Japanese Robot

AP (Apr. 24, 2014) President Obama briefly played soccer with a robot during his visit to Japan on Thursday. The President has been emphasizing technology along with security concerns during his visit. (April 24) Video provided by AP
Powered by NewsLook.com
Obama Encourages Japanese Student-Scientists

Obama Encourages Japanese Student-Scientists

AP (Apr. 24, 2014) President Obama spoke with student innovators in Japan and urged them to take part in increased opportunities for student exchanges with the US. (April 24) Video provided by AP
Powered by NewsLook.com
UN Joint Mission Starts Removing Landmines in Cyprus

UN Joint Mission Starts Removing Landmines in Cyprus

AFP (Apr. 23, 2014) The UN mission in Cyprus (UNFICYP) led a mine clearance demonstration on Wednesday in the UN-controlled buffer zone where demining operations are being conducted near the Cypriot village of Mammari. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com
Air Force: $4.2B Saved from Grounding A-10s

Air Force: $4.2B Saved from Grounding A-10s

AP (Apr. 23, 2014) Speaking about the future of the United States Air Force, Chief of Staff Gen. Mark Welsh says the choice to divest the A-10 fleet was logical and least impactful. (April 23) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins