Science Article Documents the Additive Manufacturing of Shape Memory Alloys to Create High-Performance Solid-State Cooling Technology
ADAPT researchers Nathan Johnson (PhD candidate), Dr. Cheikh Cissé (postdoctoral scholar), Prof. Mohsen Asle Zaeem and Prof. Aaron Stebner are co-authors on a paper published in the most recent issue of Science.
The article documents the additive manufacturing of a highly efficient and eco-friendly elastocaloric cooling material composed of several different phases made from nickel and titanium. The work is the result of a collaboration led by researchers from the University of Maryland, together with Ames Laboratory, Colorado School of Mines, Xi’an Jiaotong University and Iowa State University.
The key finding of the research is that while elastocaloric materials typically used for solid-state cooling show a degradation in cooling behavior after hundreds of cycles, laser melting these metals creates fatigue-resistant nanocomposite microstructures that can cycle, with consistent cooling capacity, a million times.
ADAPT’s role in this research is directly related to other work the consortium has done on shape memory alloys, specifically nickel–titanium (NiTi). Nathan Johnson conducted the in situ diffraction work, and Cheikh Cissé performed the finite element modeling. Nathan is pictured at right with the ADAPT Center's Panalytical Empyrean X-ray diffractometer. X-ray diffraction was used on the additively manufactured samples to verify that phase transformation was happening, was reversible and was not changing its behavior through many cycles. It was also used to verify different phases in the material that made up the nanocomposite microstructure.
Cooling technology, used in refrigeration and HVAC systems around the globe, is a multibillion dollar business. Vapor compression cooling, which has dominated the market for more than 150 years, has not only plateaued where efficiency is concerned but also uses chemical refrigerants with high global warming potential.
Solid-state elastocaloric cooling, where stress is applied to materials to release and absorb (latent) heat, has been under development for the last decade and is a front-runner in alternative cooling technologies. Shape memory alloys are found to display a significant elastocaloric cooling effect; however, the presence of hysteresis—work lost in each cycle and the cause of materials fatigue and eventual failure—remains a challenge.
To that end, an international team of collaborators led by UMD Materials Science and Engineering Professor Ichiro Takeuchi has developed an improved elastocaloric cooling material using a blend of nickel and titanium metals, forged using a 3D printer, that is not only potentially more efficient than current technology, but is completely “green.” Moreover, it can be quickly scaled for use in larger devices.
Takeuchi said, “Dr. Stebner’s expertise played a crucial role in developing understanding of the fundamental mechanism behind fatigue-resistant behavior of additive manufactured shape memory alloys. His group’s in situ synchrotron diffraction and finite element modeling capabilities gave us unique insight into the inner workings of the material.” Read More
Researcher of the Month
Nathan Johnson, a co-author in the Science publication discussed above, is a PhD candidate in the Materials Science program at Colorado School of Mines.
Advanced manufacturing requires equally advanced techniques for verifying the quality and behavior of manufactured parts. AM shape memory alloys have characteristics and properties that deviate from traditionally manufactured parts. As was shown in the recent Science publication, these properties can be vastly more efficient.
For the reported research, Nathan used an advanced characterization technique called high-energy X-ray diffraction to study how these advanced shape memory alloys deform, change, and behave under mechanical load. Ultimately, this technique was able to measure precise changes in the structure of the parts as they were deformed. This analysis gives insight into how the structures will perform in an engineering application.
Nathan's thesis focuses on using high-energy X-ray diffraction to study a multitude of phenomena in additively manufactured materials, ranging from solidification to phase changes in materials to mechanical performance.
Nathan’s first experiment characterized the solidification and growth of titanium alloys during the additive manufacturing process, ultimately revealing how phases change in titanium from high temperature to low temperature. Currently, Nathan is working on characterizing how additively manufactured complex geometries (called lattice structures) respond to compression. These structures can be used to improve mechanical performance while simultaneously reducing weight for important applications like ostoprotheses and aerospace components.
Upcoming Winter Social
Join us for the ADAPT Winter Social and Happy Hour! Food and drinks provided.
When: Wednesday, December 11, 1:30–5:30 pm Where: Starzer Welcome Center Boardroom (1812 Illinois St., Golden, CO 80401)