Engineers Develop Record-Breaking Steel

Thursday, May 12th, 2016
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A team of engineers has developed a type of steel with record-breaking resistance to deformation from impacts.

Named SAM2X5-630, the new alloy was revealed to have the highest recorded elastic limit for any steel alloy. SAM2X5-630 resists deformation under pressure and stress up to 12.5 giga-Pascals or 125,000 atmospheres.

SAM2X5-630 is an amorphous steel alloy, also known as bulk metallic glass. These alloys deviate from the crystalline structure present in most metals, where iron atoms occupy specific locations.

To make the new alloy, the team mixed metal powders in a graphite mold that was then pressurized at 100 mega-Pascals (1,000 atmospheres) and exposed to a powerful current of 10,000 amps at 1,165°F (630C).

This process is called spark plasma sintering and it has the advantage of producing materials faster—taking only five to twenty minutes—and using less energy than more conventional industrial processes.

The engineers tested SAM2X5-630’s response to shock by hitting samples of the material with copper plates fired from a gas gun at 500 to 1,300 meters per second. The material deformed on impact, but not permanently.

The Hugoniot Elastic Limit (the maximum shock a material can take without irreversibly deforming) of a 1.5-1.8 mm-thick piece of SAM2X5-630 was measured at 11.76 ± 1.26 giga-Pascals.

For comparison, the elastic limits of stainless steel, tungsten carbide, and diamonds are 0.2 giga-Pascals, 4.5 giga-Pascals and 60 giga-Pascals, respectively.

Further research on the alloy will focus on increasing its material weight to reach higher elastic limits and resistance to deformation.

Potential applications for this new, stronger steel alloy include drill bits, body armor, meteor-resistant casings for satellites, tank armor, ship hulls, piping in the pulp and paper industry, vehicle engines and more.

“Because these materials are designed to withstand extreme conditions, you can process them under extreme conditions successfully,” said Olivia Graeve, professor of mechanical engineering at the Jacobs School of Engineering at UC San Diego.

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