Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Research Shows Why Metal Alloys Degrade

26.09.2008
Metal alloys can fail unexpectedly in a wide range of applications---from jet engines to satellites to cell phones---and new research from the University of Michigan helps to explain why.

Metal alloys are solids made from at least two different metallic elements. The elements are often mixed together as liquid, and when they "freeze," into solids, tiny grains of crystal form to create a polycrystalline material. A polycrystalline material is made of multiple crystals.

Within each of the grains of crystal, atoms are arranged in a periodic pattern. This pattern isn't perfect, though. For example, some of the places atoms should be are empty. These empty spaces are called vacancies. Atoms of each element in the alloy take advantage of these holes in the lattice. In a process called diffusion, atoms hop through the material, changing its structure.

"It's kind of like musical chairs," said Katsuyo Thornton, assistant professor in the U-M Department of Materials Science and Engineering. "Diffusion happens in nearly every material, and materials can degrade because diffusion causes certain changes in the structure of the material."

Atoms of different elements tend to hop at different rates because they are bound to their surrounding atoms with varying strength. Thornton and her colleagues have demonstrated that when there's a greater discrepancy in the hop rates in the different elements in the alloy, there's a more pronounced diffusion along grain boundaries. This possibly leads to a faster degradation. Thornton's collaborators on this project are Materials Science and Engineering doctoral student Hui-Chia Yu, and Anton Van der Ven, an assistant professor in the same department.

"In some cases, the grain-boundary diffusion is 100 times higher than what was commonly expected," Thornton said.

"This is a very generic finding," she said. "That's why it's important. It applies to a wide variety of materials. It applies to polycrystalline materials including electronic materials like solder."

Conventional solder, made of tin and lead, is a common alloy that connects electronic components in computer circuit boards and gadgets. Because lead is toxic, engineers are working to design new kinds of solder without lead. But they haven't found a substitute that works as well. The team's findings may help explain why "tin whiskers" form in some of these new solders. Tin whiskers have caused damage to satellites, for example.

"We are trying to apply this theory to whisker growth in solder," Thornton said.

This finding suggests that materials scientists could make longer-lasting alloys if they use metals with similar atomic hop rates, or manipulate the intrinsic hop rates by other mechanisms.

A paper on the findings called "Theory of grain boundary diffusion induced by the Kirkendall effect" is published online in Applied Physics Letters. The full text is available at: http://link.aip.org/link/?APPLAB/93/091908/1.

For more information:

Katsuyo Thornton: http://www.mse.engin.umich.edu/people/faculty/thornton
Anton Van der Ven: http://www.mse.engin.umich.edu/people/faculty/vanderven
Michigan Engineering:
The University of Michigan College of Engineering is ranked among the top engineering schools in the country. At more than $130 million annually, its engineering research budget is one of largest of any public university. Michigan Engineering is home to 11 academic departments and a National Science Foundation Engineering Research Center. The college plays a leading role in the Michigan Memorial Phoenix Energy Institute and hosts the world class Lurie Nanofabrication Facility. Michigan Engineering's premier scholarship, international scale and multidisciplinary scope combine to create The Michigan Difference.

Nicole Casal Moore | Newswise Science News
Further information:
http://www.umich.edu
http://www.engin.umich.edu

More articles from Materials Sciences:

nachricht Strange but true: Turning a material upside down can sometimes make it softer
20.10.2017 | Universitat Autonoma de Barcelona

nachricht Metallic nanoparticles will help to determine the percentage of volatile compounds
20.10.2017 | Lomonosov Moscow State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>