Novel Ames Lab composite may replace deplet...( AMES Iowa -- Armor-piercing projecti...),Health

AMES, Iowa -- Armor-piercing projectiles made of depleted uranium have caused concern among soldiers storing and using them. Now, scientists at the U.S. Department of Energy's Ames Laboratory are close to developing a new composite with an internal structure resembling fudge-ripple ice cream that is actually comprised of environmentally safe materials to do the job even better.

Ames Laboratory senior scientist Dan Sordelet leads a research team that is synthesizing nanolayers of tungsten and metallic glass to build a projectile. "As the projectile goes further into protective armor, pieces of the projectile are sheared away, helping to form a sharpened chisel point at the head of the penetrator," said Sordelet. "The metallic glass and tungsten are environmentally benign and eliminate health worries related to toxicity and perceived radiation concerns regarding depleted uranium."

Depleted-uranium-based alloys have traditionally been used in the production of solid metal, armor-piercing projectiles known as kinetic energy penetrators, or KEPs. The combination of high density (~18.6 grams per cubic centimeter) and strength make depleted uranium, DU, ideal for ballistics applications. Moreover, DU is particularly well-suited for KEPs because its complex crystal structure promotes what scientists call shear localization or shear banding when plastically deformed. In other words, when DU penetrators hit a target at very high speeds, they deform in a "self-sharpening" behavior.

"It's very desirable to have this type of behavior together with high density, so that's why DU is used, but there has been strong global interest in replacing it since the start of the Gulf War in 1991." said Sordelet.

A popular replacement for DU is tungsten because at 19.3 grams per cubic centimeter, it's a little bit denser than DU. However, tungsten has a very simple crystal structure known as a body-centered cubic structure. "If I made the same solid
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Contact: Saren Johnston
sarenj@ameslab.gov
515-294-3474
DOE/Ames Laboratory
31-Jan-2007