New metal could be used for mobile electronics and biomedical devices.
A research team at the UCLA Henry Samueli School of Engineering and Applied Science has created an extremely strong yet lightweight structural metal with a very high specific strength and modulus, or stiffness-to-weight ratio. The new metal is composed of magnesium infused with a dense and even dispersal of ceramic silicon carbide nanoparticles. They say that it could be used in lighter weight transportation vehicles and aircraft, as well as in mobile electronics and biomedical devices.
“It’s been proposed that nanoparticles could really enhance the strength of metals without damaging their plasticity, especially light metals like magnesium, but no groups have been able to disperse ceramic nanoparticles in molten metals until now,” says Xiaochun Li, the principal investigator on the research and Raytheon Chair in Manufacturing Engineering at UCLA.
“With an infusion of physics and materials processing, our method paves a new way to enhance the performance of many different kinds of metals by evenly infusing dense nanoparticles to enhance the performance of metals to meet energy and sustainability challenges in today’s society.”
Structural metals are load-bearing metals and magnesium, at just two-thirds the density of aluminum, is the lightest structural metal. Silicon carbide is an ultra-hard ceramic commonly used in industrial cutting blades. The researchers’ technique of infusing a large number of silicon carbide particles smaller than 100 nanometers into magnesium added significant strength, stiffness, plasticity, and durability under high temperatures.
The researchers’ new silicon carbideinfused magnesium demonstrated record levels of specific strength—how much weight a material can withstand before breaking—and specific modulus— the material’s stiffness-to-weight ratio. It also showed superior stability at high temperatures. (See Figure 1)
Ceramic particles have long been considered as a potential way to make metals stronger. However, with microscale ceramic particles, the infusion process results in a loss of plasticity. Nanoscale particles, in contrast, can enhance strength while maintaining or even improving metals’ plasticity. But nanoscale ceramic particles tend to clump together rather than dispersing evenly, due to the tendency of small particles to attract one other.
To counteract this issue, the researchers dispersed the particles into a molten magnesium zinc alloy. The newly discovered nanoparticle dispersion relies on the kinetic energy in the particles’ movement. This stabilizes the particles’ dispersion and prevents clumping.
To further enhance the new metal’s strength, the researchers used a technique called high-pressure torsion to compress it. The new metal nanocomposite is about 14 percent silicon carbide nanoparticles and 86 percent magnesium.
For more information, visit http://newsroom.ucla.edu .
