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07:53 AM, October 23, 2019
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US Develops Alloy 50% Stronger than Steel for Bunker-Buster Bombs, Aircraft & Tanks

The US Air Force Research Lab (AFRL) has developed a new alloy named “USAF-96,” 50% stronger than commercially available steel, for use in bunker-buster bombs, aircraft and M1 Abrams tanks, among other military and commercial applications.

The USAF-96 (AF-9628) was developed by Dr. Rachel Ann Abrahams of the AFRL’s Munitions Directorate. A patent to manufacture the USAF-96 steel that is 50% stronger than steel was issued on October 22, writes techlinkcenter.org.

The low alloy steel, when thermally processed with the Air Force’s patented method has an ultimate tensile strength of 245 KSI; yield strength at 0.2% offset of 187 KSI; elongation to failure of 13%; and an impact toughness as measured with a Charpy V-notch test at -40°C of 30 ft-lb.

The new steel has demonstrated hardenability and toughness at -40°C, even with sections up to 4-inches in thickness, making it ideal for a range of applications from automotive components to structural bridge pieces to 3D printed parts for an M1 tank.

Steel with such features contain expensive elements such as Tungsten, Cobalt and Nickel. However, the USAF-96 does not contain tungsten, like Eglin Steel or cobalt, part of the formula for HP-9-4-20, which is in the Massive Ordnance Penetrator, a 30,000-pound bomb that destroys assets in well-protected facilities. The alloy can be produced using standard air-melt production processes.

US Develops Alloy 50% Stronger than Steel for Bunker-Buster Bombs, Aircraft & Tanks

The USAF-96 can also be powdered and 3D printed into components. The method used is called Powder Bed Fusion, where, a laser selectively melts powder in a pattern to create three-dimensional objects. As each layer is complete, the printer dispenses more powder on the build area, and the process continues until the part is complete.

“Many alloys don’t take to additive manufacturing very well. For instance, certain alloys will not melt and they crack a lot once you actually try to make a part,” said Capt. Erin Hager, an AFRL employee and recent graduate of the Air Force Institute of Technology’s Aerospace Engineering Program.

“In the case of the new alloy, we found no evidence of cracking. The output is similar to traditionally manufactured parts,” Hager asserted.

After a more thorough examination, she determined that the parts “matched the required 10 percent elongation indicating increased strength without becoming brittle.”

Hager explains that additive manufacturing “allows [engineers] to put weight [on munitions] only where it’s needed.” Ultimately, this “enables lighter munitions that get just as deep, so aircraft can carry more of these weapons,” she says.

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