Researchers engineer superelastic shape memory alloy for 3D printing

Shown at left is an electron micrograph of nickel-titanium powder. The powder can be used to fabricate 3D-printed parts like the lattices at right. Texas A&M Engineering

Engineers at Texas A&M University, supported by the U.S. National Science Foundation, have developed a superelastic shape memory alloy (SMA) for 3D printing. The material prevents part defects like warping and delamination that commonly occur when these materials are 3D-printed on LPBF (laser powder bed fusion)-style equipment.

Nickel-titanium SMAs are used in aerospace and biomedical applications, including airplane wings and surgical devices, because they revert to their original state after application of heat or stress. However, because of the expense and resource-intensive nature of the manufacturing process, the use of nickel-titanium SMAs has been limited.

“Shape memory alloys are smart materials that can remember their high-temperature shapes,” said Lei Xue, first author of a paper on the research and development. “Although they can be used in many ways, fabricating shape memory alloys into complex shapes requires fine-tuning to ensure the material has the desired properties.”

Most nickel-titanium materials are damaged during a typical LPBF process. The researchers used a framework to select optimal parameters to prevent defects and fabricate nickel-titanium parts that consistently have a room-temperature tensile superelasticity of 6%. That percentage is almost double the amount previously documented, says the university.

The development has the potential to increase the scalability of 3D-printed nickel-titanium SMAs. The “study can serve as a guide on how to print nickel-titanium shape memory alloys with desired mechanical and functional characteristics,” said Xue. “If we can tailor the crystallographic texture and microstructure, there are far more applications these shape memory alloys can be used in.”